The lore question's interesting because 'strongest' could mean raw power scaling or narrative weight. For Apocrypha specifically, I'd put Karna and Achilles near the top. Karna's got that whole 'invincible armor but cursed' thing from the Mahabharata which translates into insane defensive NPs, plus his Vasavi Shakti is basically a delete button. Achilles' immortality except the heel and that duel with Hector give him a weird mix of near-invincibility and a famous, exploitable weakness. Both feel like they walked out of epic poems with their power sets fully intact, not watered-down versions.
Siegfried's lore is strong too—dragon-slayer, that back vulnerability, the whole tragic hero bit—but sometimes I think the series underutilizes it compared to the sheer mythological weight Karna carries. Mordred's a fun inversion, taking Arthurian legend and twisting it into a rebellious, deeply personal grudge match rather than pure cosmic scale.
Honestly, the weaker lore might be characters like Spartacus, whose legend is more about a symbolic revolt than concrete magical feats, so his powers feel more loosely interpreted. Fran's a weird case—built from literature, not myth, so her background's inherently smaller in scope but poignant in its own way. If 'strongest lore' means 'most epic source material directly fueling their abilities,' Karna's probably the winner.