User blog comment:Goku484/Goku vs Superman, once and for all!/@comment-4698071-20130113043246/@comment-5869016-20130115033128

He is shown to have a limit(expulsion of energy in the first movie)

Anyway Broly is non-canon, and you're implying that Broly is less durable than Frieza? I'm willing to bet a planet's explosion has more heat than the sun.

It was the combination of the sun's heat, the kamehamehas, and his running out of energy temporarily which caused Broly to die.