Stupidity: The characters wish for the resurrection of just one person (Roshi) rather than everyone killed by Piccolo as would be natural (and as they do in anime and manga). Okay, Piccolo in this movie sucks at killing and resurrecting Muten covers 50% of the total body count, but they can't know that.
Stupidity: Having become the leader of the universe's most stealthy fighters, he promptly leads them in a Custer-esque noisy frontal charge into a force with known weapon and technology superiority. Zero effort to utilize ANY of their amazing stealth, just have them slaughtered so badly that the planet has to sacrifice animals to save them from extinction.
Stupidity: Rescuing Manfred and Diego from the giant carnivorous plant, Buck could have cut both wires simultaneously to avoid that unnecessary horrible potential outcome of cutting the wrong one. The wires were stretchable enough for them to have been held together to then get cut at the same time. (00:37:40)
Suggested correction: Cutting both wires simultaneously would probably cause a different effect. Besides, Buck isn't very intelligent.