Crusher was in fact, the only antagonist in the series, but there will be more antagonists soon.
He builds structures using different scrap parts, like the Giant Robot Chef in "The Jungle Horn", but no matter what, these structures are always being thwarted by Blaze. However, not all of them are thwarted, though. In the episode "Epic Sail", he makes a machine that creates waves. This structure wasn't thwarted, for example.