Champions with true damage:
Ahri (Q)
Amumu (passive)
Aurelion Sol (E execute)
Bel’Veth ®
Camille (Q)
Cho’Gath ®
Darius ®
Draven ®
Fiora (passive + R)
Gangplank (passive + R)
Garen ®
Gwen (Q)
Kog’Maw (passive)
K’Sante (passive)
Lillia (Q)
Master Yi (E)
Olaf (E)
Pyke ®
Rek’Sai (E)
Sett (W)
Syndra (W with fully stacked passive + R execute)
Twitch (passive)
Urgot (R execute)
Vayne (Q)
Vel’Koz (passive)
Yone (E)
Zoe (E)
I wouldn’t consider Yone’s E and Zoe’s E to be true damage, because it’s a percentage of the post-mitigation damage that they dealt previously so it was already reduced by resistances
Yone’s E doesn’t make sense to do any damage at all