I would say football is the most violent. Many schools have a “weight requirement” for football, even at the 10-year-old level, so when your child is playing and is body-slammed by a kid, it’s going to be by a VERY big kid and it’s going to hurt. I know it’s none of the above, but I played soccer when I was 9+. Very cooperative game, lots of team work, no sticks/pucks to be hit with, and injuries were fairly minimal.