Revenge to Jerk of a Roommate

so here is a situation. I am living with my sister and her boyfriend who is eternal student. he sits around in our apartment all day long doing nothing but working out and watching movies, and bossing around btw. but when he is home alone, he is stealing my stuff and i've had enough of that. so i want to make revenge to make him miserable. i want to hack his computer in order to do that. he is running win 10 on his pc, and he is connecting to the same home network as i am. i made a quick research on win 10 exploits, but i had no luck finding usefull information. please help!