Weaknesses

Superman has kryptonite.
Spiderman has tiny knives.
Batman has gravity
And Cat-woman’s nine lives.

Wolverine has bad-hair-days.
Underdog has Polly.
Godzilla has the human race,
And “The Beav” has Wally.

Chubby folks have ice cream.
Skinny folks have breezes.
Rats have humans, dogs, cats,
Birds, and poison cheeses.

Chapter books have fragile spines
And test-takers have zeroes.
The theme of this poem, apparently,
Knows just five superheroes.