2. Data (Operations Officer, TNG)
Lieutenant Commander Data is an android with a positronic brain. He is faster, stronger, and more agile than a human. He can easily beat practically any living opponent in a fight. Data's reflexes let him dodge phaser fire, break free from constraints, and makes him the perfect Enterprise officer to win martial arts championships, even against skilled Starfleet officers.
Data is a dangerous opponent because he is both a skilled fighter and a tactical programmer. The only thing that could really stop him is Starfleet's ethical programming.
However, not only has Data killed the Borg before, but he even showed anger while doing so in The Next Generation, with a little help from Lore and the emotion chip. And who can forget how Data helped to destroy the Borg Queen in Star Trek: First Contact?
Data easily shows that he is better than others in both simulated and real conflicts. This makes him a great ally and a scary enemy on a Federation vessel.