After some careful trawling of memories, I've managed to narrow it down to either Street Fighter II or Mortal Kombat for the Amiga, though I was so young at the time as for it to barely count. Last time I played either of those was a good 13 or 14 years back, followed by a complete dearth of any fighting games till a few months ago when a friend introduced me to MB.
Got fond memories from those days, though the Megadrive controllers we used to play (As they shared the same port type as the Amiga) were war from ideal. Better than they keyboard, at any rate.