I'm going to confront the guy who cheated on my sister
Is there something you hope to accomplish with this confrontation?
I want that relationship to end as I definitely don't want him joining our family tree.
It's understandable to feel upset with her your sisters ex. It might be best if you leave it alone, though.
I have a strong family and I feel confident I can take him and this relationship down.
There is no right or wrong answer here and it's reasonable to be mad at your sister's boyfriend and want to protect her. I strongly urge you, however, to consider all outcomes as "shooting the messenger" is a real thing and your sister might not react the way you want or expect.