This is part of why super smash bros is so good. Playing against friends who are decent but not as good as you? Play one of your secondaries. Friends are bad but learning? Play a low tier/a character you don’t ever play. Friends are casual gamers/don’t know how to play smash? Spam b moves as a low tier. No matter how good you are you can sandbag pretty hard without your opponent feeling like you aren’t trying/not having fun.