It's a known fact that the sequels rarely do well when compared to the original. There are notable exceptions to that rule, but in this instance, it fits.
The Toxic Avenger Part II has lost some of the magic (if you can call it that) of the first one. Where the first one was so bad it was actually quite fun, this one tries the same thing but goes even further with the "stupid" aspect, and that is not a good thing. The "balance" of the first one just doesn't apply to this one.
TTA Part II has its moments, but the movie as a whole doesn't really make even a shred of sense. It just seems there are two scripts turned into one movie.
Anyway...it's watchable if you are into the crazy Troma sort of movies.