Right? Nothing about him seemed really that insane or unhinged. Even killing Gamora, his adopted daughter that he appeared to care for, can be explained as him doing whatever it takes, not being insane. Even what he did to Nebula came off, to me, as just him being extreme in his desire for her obedience and perfect, like any other obsessed and controlling parent.

Honestly, he came off more as the “annoyed Titan” than anything else.