Just as a refresher:
Combo's unique combo trait is called Auto Barrage. This allows Combo to cancel the second hit of an Auto-Double (AD) into a different Auto-Double. For example, if you perform a light AD, during the first hit of the AD press a medium or heavy and Combo will cancel the second hit of the light AD and instead perform a medium or heavy AD. You can continue this endlessly (until the KV Meter maxes out, or the combo is broken), however if you press all six buttons in any order during an Auto Barrage (light punch and kick, medium punch and kick, and heavy punch and kick), Combo will unleash his only damage Ender.
For example, let's say you open with the Spin Fist, then press light punch for an Auto-Double. After the first hit of the AD you press heavy kick, then after the heavy kick connects you press medium punch, then light kick, then heavy punch, then finally medium kick. After the medium kick, Combo will automatically go into his damage Ender.
If this seems a little too good to be true, rest assured it has been properly balanced. First off, Combo's Auto-Doubles are a little slower than other character's Auto-Doubles. It's a little easier to break them, but with Auto Barrage you should only see the first hit of an Auto-Double. In addition, the longer the Auto Barrage carries on, the slower the attacks get and the easier it is to break the combo. Attacks get even slower if you use the same button more than once. For example, if you press light punch multiple times in an Auto Barrage, the second light punch may be as slow as a heavy Auto-Double depending on when it's used.