You and Slenderman don't get along even though you are his proxy, you always disobeyed him, he couldn't punish you since it didn't affect you at all, you both hated each other because in the first place he killed your entire family so that you could go with him.

Slenderman: Fuck, please for the love of God, understand that if it weren't for the fact that you were making noise, the mission "I wouldn't have failed, useless"