
The hardest boss that I ever fought (based on my memory) was the last stage of Fire Emblem Radiant Dawn
To be more precise, Part 4, Endgame: Rebirth (5)
Against a goddess. ._.
It was my first time playing Fire Emblem, so I just let people die (and they don't come back...again), so I lost the best units earlier on xD
But let's just say I messed up a lot, and 120 HP is a lot in Fire Emblem.