Grudge is quite difficult to be interesting about; he's a great utility infielder, but on his own, he's, well, pretty straight-forward.
According to the Official Bio:
Parnell Tarrant wasn’t loved, or even liked, but he was respected—a capable scientist and researcher, but a man who knew how to hold a grudge, and repay every slight. He spent most of his time working in his field of radiation and its effects on cellular mutation, and cataloging the list of people whom he’d show up one day. Then the accident: fired up with anger, careless with rage, and exposed to his own radiation bombardment, his cellular makeup transformed. Dr. Tarrant didn’t just hold a grudge, he was Grudge, and he would show them ... show them all!
Text quoted with the permission of Steve Kenson and Ad Infinitum Games, and is not intended to challenge the copyright.
Somewhere in the ruins of Parnell Tarrant’s apartment house is a set of small black notebooks. And looking in them, the PCs can find the list of everyone who has ever offended Parnell Tarrant. Parnell was in his mind scrupulously fair: many of them list dollar values—Parnell’s estimate of the cost of the offense. These tend to be offenses like slow service at a restaurant or incorrect change at a store. (In his mind, he thought he was being fair, judging how offended to be at each wrong.) Other offenses, such as a poor grade, are priceless. The series was already at a dozen notebooks when Grudge happened, and only ten or twenty names had been stroked off. But that doesn’t matter: Grudge will make them all pay.
The key is not that Tarrant bore grudges against so many people, but rather that anyone can be a target for Grudge’s fury, whether there is an actual offense or the person just reminds Grudge of someone, such as that waitress who got his coffee order wrong (she had just learned her mother had Alzheimer’s), or that professor who gave him a low mark and delayed his early acceptance to graduate school. Though there will be specific targets who show up whenever Grudge thinks of them, anyone can be a target.
The biography doesn’t indicate whether the transformation is permanent or temporary (Solomon Grundy or the Hulk, so to speak). Because Grudge has Science listed as a Specialty, I've decided that Parnell is mostly Grudge, but there are times when he's not. Maybe Man-Bat is a better model—maybe there are times when he's not Grudge, but we only want to tell stories where he is Grudge. (I suspect that even Parnell’s mother loved him more as a duty, which might give you a whole different set of stories: does Grudge want revenge against even her?)
Continuing the Man-Bat model, we only see Tarrant at the end of stories, but he’s probably Intellect 4 when he appears. He likes to think he’s brilliant, but the word that keeps being used is “capable.” And in some ways, I think he likes being Grudge: Grudge has the freedom to deal with the petty irritations that bother Tarrant every day. (That could make a nice prologue to a Grudge adventure, though: give the players character sheets for prison transfer guards—use the Police Officer or Soldier stock characters from ICONS, let Tarrant manage to disable the power neutralization equipment, and escape after turning into Grudge and beating them up. (The players will not treat with Grudge with kid gloves after that.)
His Goals and Strategy
Grudge doesn't have deep motivations: anyone who has ever wronged him or slighted him, anyone whom Tarrant imagines has slighted him, anyone who reminds Tarrant of a past slight, is a potential target.
This simplicity of purpose makes Grudge a useful tool for other villains. It means that you can justify a partnership with almost any villain at least once. Many use him just as a diversion (as in Grudge Match), but some might actually team up with him, or hire him. ConfederApe uses him, but finds a sense of superiority in using him. The Creeper understands what it's like to be laughed at. Troll rather likes fighting him—there's no real danger, but it's a great workout. Warbride thinks he's sexy, in a dirty uncontrolled male kind of way. Heck, I imagine that Ultra-Mind finds him to be a useful gross physical tool, and probably romps through Tarrant's mind regularly, making sure that there are no past wrongs assigned to the Ultra-Mind.
The PCs might have a relationship with Tarrant; that makes his story a bit more tragic. Or you could use him to point up the idea that superpowers don't change a man, only refine him into a pure form of what he was, before. That might make some PCs take notice of their current behaviour.
- The players have the list of people against whom Tarrant bore a grudge…at least one volume of it. Do they go and protect all those people? (Bonus Determination to the PCs who come up with clever ways to prioritize.)
- Grudge has worked his way down to movie reviewers. A website specializes in inflammatory (but not legally actionable) comments that get page views, and Grudge takes exception to the review of his favourite show, which the reviewer thinks has jumped the shark. The comments section contained a number of items from Grudge, but they have been ignored or worse. Now Grudge takes things into his own hands, but getting the physical address instead of the computer address is taking some work. First, beat up and threaten a computer professional… Do the PCs wait at his eventual goal, or try to stem the intermediate mayhem?
- Grudge bears a, well, grudge against anyone who has ever teamed up with him and caused him to lose (from his point of view). But he's not stupid (certainly not Bizarro levels of stupid). So he has a cunning plan&mdash:well, cunning for Grudge. He’s going to throw them over, so the PCs keep receiving notes from Grudge (possibly in crayon, because he breaks pens and pencils) about the location of the crimes to be. Except, of course, the other villains have figured it out, and Grudge keeps getting caught alone. Do the PCs help Grudge trap the other villains in the name of catching them, or do they suspect it’s actually a trap set by the other villains?