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Has it ever occurred to anyone on this show to just team up and/or go into their final form and just beat the crap out of the villian of the week? If this has been said before do they just ignore it like they are saiyan nonsense?
Vegeta often throws common sense out the window if it means he'll get a more challenging fight. "Oh, you have a stronger form? Ok, you can transform into it. I'll even beat up my son so he can't stop you!"
Full power is physically taxing and doesn't last very long, while everything below that is almost effortless. Teaming up has happened but it doesn't really do much, if you really want to combine your powers you're better of fusing.