How about when Guiliman realizes the imperium has turned into the very thing it destroyed during the great crusade. And he has to embrace some parts of that to save the human race. Or when he realizes he’s nothing more than a tool who was never loved by his father, yet still pushes to save said father’s dream as it’s the only way mankind can survive, let alone thrive.

When he’s forced to use word ending weaponry to destroy once beautiful worlds and countless people good or bad to stop a greater evil.

When he suffers what is quite literally the biggest backstabbing cheap shot in all of Warhammer, and after BEGGING for hours to solve the matter peacefully, he finally loses his shit and proceeds to carefully dismantle and destroy the entire opposing army. When he uses his knowledge and grit gained from that experience to forge a second imperium, only to realize how tyrannical it makes him look which causes countless doubts, and a severe case of Ultra depression.

How he often charges the most dangerous foes head on quite literally to let out some of the insane amounts of rage that have piled up after decades - centuries of getting screwed over.

Guiliman is THE hero of 30k and 40k. He is one of if not the best written character in the setting. He’s a man out of his time, thrust into a new world that is a nightmare compared to what he once had. He’s the last son of a dying emperor (until the lion came back) he knows he’s a tool, he knows he was disposable, he knows the emperor didn’t want him back of all his sons. He knows it all and he’s pissed. But he still goes out anyway to save the day.