This is a very unpopular opinion, but Soldier.
First of all, blast radius. It’s way too large and the fall-off is not substantial, so just hit light or mid class with close range blast radius 2 times and you win, wear the gunboats to perform the “shoot my feet, get points” trick. Classes like Scout almost stand little chance if a Soldier knows how to abuse it enough. And one could say “Don’t get close”, but the Scattergun vs the Rocket launcher at mid/mid-long range is no contest, considering the rocket launcher requires less aim, does more damage, and the small, but considerable fact Soldier has 75 more health. So mid range fight with both competent players is just a high chance of Soldier winning. Unless the fight zone has areas the scout can jump ontop of, then the chance is rather equal.