Bug-Eaten

Bug-Eaten (虫喰い) is a Stand-using brown rat from Part IV: Diamond is Unbreakable. While it has no evil intent, the rat has a natural instinct to eat and goes after even humans as a food source.

History
While Akira Otoishi had Keicho Nijimura's Arrow in his possession, he tested its powers by using it on two rats. The arrow pierced the rats, granting them both the Stand Ratt.

Believing that only one rat exists, Jotaro Kujo and Josuke Higashikata go hunting for it for damage control after Jotaro questions the defeated Akira. In the process, the two rats had managed to meld together the bodies of other rats into cubes of flesh.

Diamond is Unbreakable
The two protagonists follow a drain pipe to an empty house and discover a rat in the kitchen in the process of testing its Stand ability on humans. Josuke quickly disposes of it, but is surprised by the presence of the second rat, whom Jotaro names Bug-Eaten. After moving their battle outside, a deadlock commences with both sides refusing to move from their cover. Bug-Eaten is eventually shot and killed when Josuke tricks the rat from moving from its cover.

Trivia

 * The hole in its ear is likely a wound from the Arrow, making both rats stand users.
 * "Bug-Eaten" is a name given by Jotaro, referring to the hole in its ear.