Probably as good as you could reasonably expect from a full-on belt-scrolling brawler on the original Game Boy. Certainly could have turned out worse.

The combat is fine with a surprising amount of moves (two-button uppercut, ground finisher, and a grab in addition to the standard punches and kicks) but every animation is agonizingly slow, making you feel like you're fighting in knee deep mud. Thankfully, the enemies aren't any faster with their (sometimes quite impressive, actually) attack animations, so once you account for the general slow speed of combat, it becomes second nature. Actually, most of it quickly gets like that, because all the enemies (including every boss) require essentially the same rudimentary strategy to defeat, so as soon as you get that standard approach down, it's repeat all the way to the end of the game. And with the relatively stock enemies^ and levels (some of the latter of which are repeated, shamefully) that means a pretty boring, long run. At least it's easy.

They have such a solid framework here that it's a shame they didn't do anything more to spice it up. It really wouldn't have taken much. But it does deserve some minor praise for being a complete and playable brawler. I wonder if the JPN Kunio-Kun version is any more interesting.

^The level bosses in this game follow the age-old, logical progression of Boxer -> Jason Voorhees -> Ninja Master -> Italian guy