that he considered murdering and thus set off a chain of events that created a evil that is responsible for the killing hundreds of innocent lives.
That isn’t what happened.
Yes it is. Luke considered murdering Kylo which caused Kylo to go full dark side. Doesn’t matter if Snoke had already corrupted him, Luke showed us in RotJ that no one’s ever truly lost, so if he acted different he would’ve possibly saved Ben. However, he considered murdering him, which caused him to go full dark side, and that indirectly killed countless innocent lives.