Here are the statistics for the NPC Giant Rat from Warhammer Quest for iOS.

Statistics for Giant Rats
Wounds 2
Movement 6
Weapons Skill 1
Ballistic Skill 1
Strength 2
Toughness 3
Melee Attacks 1
Ranged Attacks 1

If a Giant Rat performs a Deathblow attack against your warrior in the NPC's attack phase, your warrior will be able to return the attack and, because of their low Wounds score, they will usually be killed. You can use this weakness to your advantage in battles against a large number of enemies, focusing on other creatures first (like Giant Bats) with the view that you can probably mop up a few Giant Rats during their attack phase.