Cinder's weapon is boring I also agree. It's just so normal for a villain character. In the hands of a supporting cast it'd be fine, but Cinder's pretty hyped up, she needs more wow factor.

I think it's too soon to call out on her "underdevelopment" though. We've been given suggestions as to what kind of past she's had through her dialogue, so that means they plan on revealing her backstory much later.