I actually tried for like half an hour to whittle down Bahamut at Dragon's Peak in the original FF3. It's not like I wasn't familiar with him - I had already played FF4 by that point, and I knew he was supposed to be a big tough monster, but he didn't hit all that hard and I did some damage, so I assumed I was supposed to win eventually. Then I ran out of healing items and such, and that's when I remembered Desch telling me to run, and I couldn't have felt dumber.
Supposedly it is possible to beat him here, though.