Between protags
1) Red (lore-confirmed the best trainer)
2) Brendan (dealt with bioterrorists, took the task to calm two rampaging legendaries)
3) Gold (isn't confirmed if he defeated red or not, but yet, he got to be the champion in two regions)
5) Lucas (he went into the distortion world and faced Giratina, confirmed by the canon. Also faced the lake trio and Dialga/Palkia canonically)
6) Hilbert (Confirmed legendary capture, dealt with probably the most powerful evil team leader) / Nate (almost the same, didn't really play BW2)
7) Kalm (faced Xerneas/Yveltal, first to master mega-evolution canonically and his evil team leader did too, but his region is weak in general and didn't do much more during his adventure)
7) Sun (Protected his region from an extraterrestrial hazard, but yet, can't compare him much to others since fighting isn't really much of a thing in Alola because they don't have gyms or a league)
Non-protags: Lance for being the most renamed E4 and also a champion, every other champion, Blue as his own mention, Caitlin for being in both E4 and Battle Frontier, Volkner and Koga for being E4 level gym leaders according to the lore, Giovanni as a country's most terrorizing criminal who's also a gym leader, Iris and Wallace for the same reason, and i'd like to mention Agatha)
>also>>37414878t. pic related