It depends what sort of "greatness" you have in mind. I had magus who was a member of a tiny ex miscellanea group who wanted to revitalise the tradition - so I took Good Teacher and a load of xp boosting virtues. Secondary Insight was a poor buy in the short-term, but long-term gained me enough xp I had decent totals in many arts, which I wrote good tractatus about, and gained a solid reputation as an author and was able to trade with other covenants for a great many things.
For other things - pick your angle and aim ruthlessly for it. If it's to be the greatest combat magus, work on that penetration and parma and your main arts, and gain spell mastery. If it's to be a great mystery cultist, have the Presence and take Independent Study so you can practice or adventure your way to a higher Mystery Cult Lore than there are books or teachers for.
There are some differences between creating a single Magi and a whole Covenant destined for greatness as well. I'll hit that up at the end.
You should be looking for V/F and a design that improves long term advancement rather than immediate power out of gauntlet. Sure there are V like Affinity that everyone takes, but there are others. You are specifically looking for things that ether boost XP gained or longevity (primarily by reducing Warping). Book Learner for example is actually a large boost to long term development, since with it even poor books produce a decent return when studied. Flawless Magic does both, giving bonus XP (though in a limited area) and greatly reducing the amount of spell botches (thus Warping). If you can swing the points, SFB is actually good since it delays the time when a Magi must first use a LR by 15 years (and makes them more likely to survive aging), gives an attribute point to round the character out, and makes them native to Faerie Auras (they gain Faerie granted Second Sight). Note that I do not mean they have Faerie Magic. Rather they do not gain warping points from living in a strong (6+) Faerie Aura and is partially immune to the additional botch dice (see example in "Realm Interaction" AM5, p.183).
Another thing to consider is that you do not need to be a single Art or TeFo specialist if built right. Since you will be good at learning everything, unless there is a reason to heavily study some specific Art (like a spell you want to learn or item to enchant) you can study the highest quality book your Covenant has available. All the generalist in long term games I have played end up with more total XP in Arts than the specialist (even ones with Affinity) because they are much less limited in the books that they want to study.
When you go for a Covenant destined for greatness things get really interesting. Darkwing brought up Good Teacher. If most (or all) the Magi in a Covenant end up with Good Teacher and Book Learner, just by setting up a writing exchange between themselves they will rapidly advance in power.
For greatness your goal should be long term power and capability, not the most you can gain right out of gauntlet. If you build for the most power out of gauntlet you might be more powerful short term but later in life you will be surpassed.
I am ambivalent on Book Learner and its ilk.
On one side, it takes you 8 seasons instead of 10 seasons to reach score 15. Which roughly means with the same effort you end up with +2 to every Art.
On the other side, that's a +5 Lab Total for whatever TeFo you want. Saving a season of lab work never looked "mighty" to me. I had a Boni who pushed for this and I didn't feel an impact. I'd still pick it every time, but it's just a number.
"Destined for greatness" is more about what other magi couldn't do. Picking the right MMF, building faerie sympathies, being at the right place at the right time with a Reputation to leverage it. It's all about building a story, creating a myth.
Mighty Aqua Maga? Freeing Doggerland from its faerie curse would be great.
You can achieve it with a lot of of min-max optimisation. I saw one thread where someone was designing a character who could live to 300+. That characters numbers would be insane. They'd clearly have lots of spare time for searching for breakthroughs, inventing a signature spell or item, searching the world to discover something amazing, etc.
There is an option if you don't want to go full Grognard.
If the destined for greatness magi is an NPC, or the players are happy to go with it for one or more PCs, an option is to make unbalanced virtues.
Let's look at Bonisagus. Hermetic magic and the Parma are breakthroughs that took him years. How long would it take him to then teach Hermetic Magic and the Parma Majica? How long would it have taken for him to improve his Parma Majica to the point it would be a decent defence. Anything less than 3, considering the narrative has Bonisagus meeting the most powerful magi of their time doesn't seem good enough. Let's add all his travelling the world to meet the other magi as well.
I know he had help, but he did a lot. It's hard to see how Bonisagus can achieve what he did in his lifetime without some broken virtues.
Let's invent a broken virtue for Bonisagus.
Masterful Insight (+3) - When attempting to achieve a breakthrough roll twice and take the best result. When the magi achieves a skill related breakthrough, the skill starts at level 6 (edited to 6 after a comment below), all XP for breakthrough skills are doubled. When the magi teaches a breakthrough, the student gets double XP.
That makes what Bonisagus did look plausible. Founders are extraordinary, and arguably, while our players are the centre of the narrative, they are no more special than any other magi, at least RAW character creation, so getting to the standard of a founder needs something special.
Time amplifies the qualities of someone. All Bonisagus needs imho is Int +5 and Inventive Genius. He probably acquired different forms of Hedge Magic Theory along the way, and then performed a mix of original research and integration to create his own, improved skill, integrating different things he picked up at first, and then things that were taught to him by other founders. Puissant Magic Theory could be a transformed Puissant Hedge Theory he started with, or simply have been acquired along the way.
“The ability starts at a score of 3” is weaker than what one gets by RaW which is an xp per breakthrough point earned meaning 30+ xp in a minor breakthrough (not usually an ability but if it is it’s a score of 3), 45+ for a major breakthrough (often a Sup Ability), or 60+ for a Hermetic Breakthrough (often a new Arcane Ability, the kind Parma Magica would have been). So Bonisagus would have had a starting score of at least 4 in Parma Magica.
While this thread has been rather instructive, I had been thinking more of an NPC mage, rather than a PC (though thanks to this thread...).
I had been thinking along the lines that they may have a Death Prophecy that involves a threefold death, usually reserved for the great or powerful.
Or has Luck, indicating their sorcerous (or sortilegious) potency can bend Fate in their favour. As far as I understand, Luck works in Experimental extraordinary result, Aging rolls, and Twilight rolls.
One possible tell might be they have Side Effect - temporarily increase the Magic Aura by +1 within a pace or two.
None of those are places I see luck applying to rolls. Extraordinary Results aren’t a linear table and Luck should be determined as a bonus before the roll, Aging rolls take into account quite a bit and most of it is skilled (LRs, Medicine, etc.), Twilight Rolls I just don't see how you think luck is a factor at all.
Greatness in the eyes of the order? Or greatness in the eyes of the SCs? For the order he just need a fitting reputation and some deeds he is known for. Otherwise he could be mysterious (lol or even a fake like Gilderoy Lockhart from the Harry Potter Series).
Does he needs virtues and flaws in the beginning - proably not, just when the players meets him and interact it could be necessary. And it would depends on the stories involved and why he is in the stories.
More important for my would be to define his stories and his behaviour toward the SCs.
Greatness in the eyes of the player is more difficult and depends on them - at least for me I introduced so many nps which which was completly otherwise interpreted by the players as intended (arrogant instead of helpful and vice versa, nice instead if untrustworthy, and vice versa ...)
sounds nice, he could survive something which he shouldnt. And maybe later the PC need to get rid of him ...
writing about it, I should create such a guy for my campaign - so any ideas for stories and why he is great would be welcome.
As a starting NPC mage he should be somehow in permanent competition with some/all the SCs or personal known (maybe trained in same convenant as a SC) and they hear all the time of his great exploits...
Greatness of founder quality is clearly not about great spells and enchantments. That would just be filling into the framework of the founders. Rather routine, let's admit. Thus we must be looking for true originality. I see just two immediate approaches
Hermetic Original Research, where you need to put all you can into Magic Theory (affinity, puissant, and whatever you can find).
Experimental Mystery Initiations, where you need as much presence and cult lore as you can get.
Little else matters, although a long life would help, so strong faerie blood and death profecy and unaging are good. Then, of course, you need luck. Not sure how the Luck virtue works in practice, but that's a good idea too.
The big challenge, I think, is to think up the original ideas that need inventing ... is there anything left that was not invented centuries ago?
However, one should remember that the founders' achievements were not individual acts; they depend on the particular constellation of founders with complementary abilities. Bonisagus' Theory brings together all the others, and is nothing on its own. Parma Magica is great, but the fame comes from the collaboration it facilitated. Hence, maybe, the greatest ability to prioritise is the social and political skills to get the best out of everybody else. Tremere might be the only magi able of such greatness today, thanks to their collaborative spirit.
I was wondering if you could to this as a curse, not unlike King in One Punch Man, or a variation on Mistaken Identity.
So someone who gets attributed lots of great deeds, with appropriate reputations ("Someone slew the dragon!" => "It must have been Xanax the mighty, I heard he was around"), without actually having done anything.
To make it worse, the real persons behind all these deeds might hate the Great Magus, with everyone around them thinking they're just jealous and wanting to steal their thunder ("Since I told you it was I who slew the beast!")
If you want a mighty-looking magus, then look at the rules in Covenants for lab specialisation and work on increasing your aesthetics. The magus with the impressive building set aside for his use, with a fancy archway with guards stood outside, with a studio showing off his works, and the most impressive internal features will gain a colossal reputation. (I had a magus put a magical gangway on his flying boat so he could claim the airborne and impressive entrance bonuses).
It occurs to me, that with a co-operative SG and troupe, Latent Magical Ability could give quite a potent mechanical advantage.
One interpretation is basically the recipient has a magical virtue above and beyond what their parens could teach, only emerging under the correct stimulus.
Perhaps something that even shortcuts a Hermetic Breakthrough? I should probably dig up the Hedge Magics book, if that is the one with suggestions on Hermetic integration.
Rival Magic also has some integration suggestions as does Ancient Magic. I figure Latent Magic Ability should usually be replaced with a minor virtue, not that that makes it low powered since sometimes a minor virtue works quite well with other virtues or powers.