Who are you to dictate who lives and who dies? You are no GOD, you are no SUPERIOR, you're just a petty little punk who decided to do an awful thing and tell that person you're bullying to kill themself. You don't decide such things, so don't go playing with such things. Be better than that.
And if you're that kid who's doing that think and you're depressed too:
1. You should no better
2. There are other things to do to ease yourself and your situation
3. If it ends up being them dying too, trust me, you won't feel much livelier
4. Do what you can to do the right thing anyway. Don't be the thing in the world you hate. "If I'm gonna burn, I might as well be bright."