I like to break up relationships
That is awful! Why do you enjoy that?
I like the feeling to be free when I'm single. It feels like I can do anything when I'm single.
Just because you enjoy being single doesn't give you a right to assume thats best for other people. You shouldn't get involved in a relationship that isn't yours.
No one cares about them. It's not like anyone will even know.
It doesn't matter if no one knows what you did. It's still wrong to involved yourself in someone else's relationship in to ruin it. People have a right to decide how their own relationship should end without you interfering.