A group of viltrumites? Surrender immediately. We’ve never seen what happens if a planet does that, but with no way to fight back it can’t be worse than the alternative.

They could also bring weapons and armour into battle, or bombard their enemies from orbit. But that’s not the viltrumite style

I agree on the star wars point but I think that generally the Jedi could cause them serious trouble. Lightsabers can definitely cut viltrumites to pieces and it doesn’t matter how fast you are if the force tells your enemy where you’re going to be. I think if a viltrumites just rushed a Jedi they’d end up cut in half and the Jedi would end up as a bloody smear on the pavement.