#5: Death of Cliffjumper (Transformers)
I know we didn't know a thing about the guy, but he died a heroes death.
#4: Death of Mothra (Rebirth of Mothra)
Mothra saves her son Mothra Leo, but drowns in the process. This one is sad because Mothra was a very kind mother.
#3: Death of Burai (Kyoryu Sentai Zyuranger)
Burai's left was bound by the Green Candle, kept hidden in the Lapseless Room, which was destroyed by Bandora ,killing Burai.
#2: Death of Godzilla (Godzilla vs Destroyah)
Godzilla, who is on the verge of nuclear meltdown (which would destroy the whole Earth), losses his son, who was killed by Destroyah. Godzilla retaliates be killing Destroyah. Finally, Godzilla begins to melt, and the humans use special freezing weapons to keep Godzilla from killing everyone. Godzilla melted right before my eyes. As a child, it was like watching Superman or Optimus Prime melt to death. Thankfully, Godzilla's son is revived and becomes the new King of the Monsters!