Here's the original track from the NES game. Startropics as a whole had a lighthearted vibe so it's unsurprising that the boss theme wasn't particularly intense. The game was a fun action platformer, so even though the monsters were "evil", it made more sense to arrange the track with that emphasis on action. The title Locked In with Evil is just because Boss Battle sounded kinda boring.
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Maroo
Sounds like a (Boss-)fight theme for a video game. As such it is nicely done. But i for one don't get the "evil"-feeling from it. For that it would have to be slower and perhaps indicate the feeling of impending doom through lower pitched sounds. Sorry if this doesn't make much sense. English isn't my native tongue.