How bad is it? It's a ridiculous low-budget film that rips off "The Killer Shrews!"
Should you see it? Sure. It's a fun ride.
I left this film off the list until now because it's not terrible and it is enjoyable. Grain contaminated with steroids causes rats to become giant killers (and somehow smarter). The rats are portrayed by dachshunds wearing rat costumes and there are times when you can see they had trouble getting the dogs to "attack." The acting and direction aren't bad compared to most films on this blog, but the dogs-dressed-as-rodents idea was used in The Killer Shrews a generation earlier and it hasn't improved.