I was horrendously underleveled at the end of the game because I didn't think to level my guys up to 20 before promoting them. Because of this, they were really really weak (also the fact that I didn't level Lyn, Elliwood, or Nils at all didn't help since you have to bring them into the final fight). Most of my guys I brought were the ones you get later in the game that are already pretty strong. The only one I brought from the beginning of the game (Besides to ones I had to bring) was Erk and Lucius becuase they rock at magic. I think my guys were around level 15 or 16 promoted, but they were promoted at around lecel 13 or 14, so they definitely weren't up to snuff. I had to run away with all my weaker characters. Nils was a pathetic level 5 or something. Jaffar, Hector, and my mages did most of the smashing. Hector was the only one I waited until lvl 20 to promote him. I think he was like level 6 or something promoted, but was still strong as hell.