@SayuriArtsy Side note: I'd say the speed and dmg/weapon upgrade would be temporary. Like if you get hit, or drop the kill combo it drops down a level or resets back to base form.
@SayuriArtsy I'd say speed/damage. I imagine the pacing of Starfox64 and if I was doing well clearing enemies out of the way that the game could speed up the pace give some sort of attack upgrade and increased difficulty by either adding more enemies, & harder enemies to keep speeding up.
@SayuriArtsy And maybe if you clear through a level fast enough there's like a gate/warp that's only open if you get there fast enough to go to an alternate area in the level, alternate boss or a different route on the level map.
@SayuriArtsy If I may ask, what genre of game are we spitballing for here to get a sense of direction. Like are we dealing with a fighter game like smash bros Or street fighter. Or like a hack n slash like devil may cry or Kingdom hearts even.
@SayuriArtsy I'm not sure of the scale of the fights or their areas, but it could also go to charge a dash to close the gaps or a damaging move to deal with tankier foes
@SayuriArtsy Well, I can see either like a damage multiplier just to keep fighting.
Some skills/attacks that can only be triggered at certain combo thresholds.
As far as resources like item drops from monsters, maybe it could increase drop rates for harder to get materials/items.