(Confession) how bad can this be?!?!

OK so I just want to tell u a little about my story I have a sister she been dating one of my friends from high school since last year he's 20 and she's 17 so at first it was OK but now bro😫 I want them to break up sooooo bad I can't stand this guy anymore 😒 he smoke and he does every type of drugs like the dragon? (I don't even know what's the dragon) he does "lsd"? He does weed pot bars so he does every type of drug the guy don't have a job he doesn't even go to college bro he acts like he's 16 years old and he's cocky as f*ck. and he's annoying he's a pain the freaking ass and he doesn't have any respect for her you know what I mean? Like the guy he tells me how they have sex or what positions they do (even tho he's talking about my sister) 😒 so he's basically a loser but my sister sometimes she wants to break up with him and sometimes she doesn't (and I know this it's up to her) but there's got to be a way last week I was talking to him in my car so this idea came to my mind "if I seduce him and make him cheat on my sister and I tell my sister he started" maybe they can break up but then I thought the guy is ugly as hell and my sister can hate me if she finds out and I don't want to risk it he has not only made drugs but he sells them and besides that he has steal from Waltmart and target one day they caught him but he didn't go to jail (unfortunately) but it's just that I can't even stand him with his presence he stress me out just by breathing so it's really bad (it's so bad that I've been thinking about doing witchcraft and see if they break up) So please understand me there's nothing coming out of this relationship and I want this to end fr so any help? 😭😭😭 I don't want my lil sis to date this guy no more because I don't care him being ugly or being rich but he has so many bad habits and flaws and he lies too much and my sister has told me so many bad things about him and she wants to break up with this guy but she says she can't... so any advice?