Big counters to Yorick because his ghouls basically feed him:
Tryndamere: Ghoul comes close --> more rage ---> more heals and or crits
Nasus: Q will get the bonus dmg if it kills the ghoul ----> feeding Q ----> 1 shotting people wait WHAT?
Trundle: Pretty sure his passive works with the ghouls too
Cho'gath: Same, pretty sure passive works with ghouls dying
So, basically all the champs that get power with killing stuff are good against Yorick. Nasus and Trynd are considered the "hard counters" to Yorick, but tbh he isn't truly hard countered by anyone. Those champs just have a lot easier time against him.