Early Sunspot's power is mostly about strength.

Early Sunspot's power is mostly about strength. He absorbs solar energy and uses it to power up. He isn't automatically a flying human flamethrower just because of the name or the way his body looks when he's charged. He's also strong without being invulnerable. Those aren't the same thing, and the early stories keep putting him in situations where that distinction matters. He can hit something incredibly hard and still get hurt himself. His energy can run down too. Having the most muscle in a particular fight doesn't mean he can keep using it forever. That gives him and Sam a useful contrast. Sam has protection when he's blasting, while Bobby's strength doesn't automatically protect him in the same way. They're both learning limits, and both can get themselves into trouble by treating a power as an answer to more problems than it actually solves. Bobby's temper adds another problem. If he gets angry before he thinks, he can do much more damage than an ordinary kid losing his patience.