Is the guy without spikes on his shell koopa or kopatropa?

The guy without spikes on his shell is a Koopa. Koopa Troopas are the standard turtle-like enemies in the Mario series, typically characterized by their smooth shells. In contrast, Koopatrols, which are a type of Koopa, have spiked shells. Therefore, if the character has a smooth shell, he is a Koopa.