Yeah, Plastic Man usually comes off as a joke but as several storylines have demonstrated he's actually incredibly powerful when he wants to be. His powers are one of those ones that sounds unimpressive on the surface but get progressively stronger the more you think about them, until you realize that he's actually an immortal, nigh-invulnerable, regenerating shape-shifter with immunity to anything that targets biology, including telepathy and undeath.
And even using his weaknesses only results in temporary incapacitation; he recovers just fine once the weakness in question (extreme and rapid temperature changes, certain chemicals) is removed. Plastic Man cannot be stopped, only slowed down.
