Enemy disadvantages are good and bad, in my experience. He are the good, the bad, and the ugly of enemies.
Enemies are good when:
- the keep you on guard. If enemies mean you can't really relax or let your guard down, they're a real disadvantage. If it means the routine tasks for folks without enemies - getting gear, leaving some stuff behind in town, going shopping, finding a doctor, etc. - are not always done without problems from your enemies.
- they are additional trouble. If Enemies make your life more difficult over and above what someone without Enemy would have, they're a real disadvantage. "Not only do you have to figure out where the Feds have stashed that witness against your boss, but your old enemy Detective Colombo is in town and asking questions about you. The clock is ticking, so get to work but don't get nicked!"
- they limit your options. Like all disadvantages, Enemies should limit your options. Some places, some choices, and some actions should be off-limits because of them. "I can't go to the cops, because the Marshals are after me!" or "We can't ask the Priest of the Good God to help, because the priesthood talks to the Inquisitors and they're hot on my heels." That kind of stuff is gold.
- if they direct your actions at least part of the time. They force you to pro-actively move to limit the damage of your enemies. You want to have sessions when you show up and think, "I have to get some work in on my enemy so things don't get worse!" and that seems like the best possible course of action.
- they cause indirect damage, sometimes. They don't just show up every session and force you to draw down on them in a fight. Instead they sometimes wipe out your NPC allies, or spread rumors about you, or put up wanted posted with your name on them, or DDOS your character's website, or show up in disguise to your hireling hiring fair and discourage people from signing on.
Enemies are bad when:
- they replace normal trouble with specific trouble. In other words, if rolling the appearance of an enemy means "Instead of the normal adventure, today you fight your enemies" then it's just normal gaming troubles with a different face. If it isn't additional trouble over and above what people without Enemy would face, then it's not a disadvantage over and above everyone else. If it's free points for everyone (Everyone has the same Enemy, and adventures are always about facing that enemy), that's not terrible but it's just a campaign approach not a problem per se.
- they are just combat foes. 100% of the players I have ever played with regard having to fight things as a positive. Problems that can be solved with violence, especially lethal violence, are not problems for them. Let me repeat that number - 100%. If an Enemy appears and the players thing, great, we can solve this once and for all by killing them, they aren't a disadvantage. (Editing later: I mean solving them as a problem for a session, not removing them as a disadvantage without paying points to do so.)
- they have no deeper impact. If the Enemy doesn't warp the way you play the character, they aren't a good disadvantage. No one hunted by the Mafia or the Red Wizards of Thay or by the assassin cult of the druid-priests of Tecla or by Mario has a normal life. Enemies that don't impact you except when they show up and cross swords with you aren't really doing much for you as a disadvantage.
- they're too strong or too weak. If they are so strong you can't ever make an impact on them, they're not really a solvable problem and thus have less impact on you (why bother, you can't weaken them). If they are so weak it doesn't matter if they bother you, so you don't care if they are dealt with or not, they're valueless. Even if they are not too strong or too weak on paper, if they are too strong or too weak in actual play, they are bad.
- they give you points but disadvantage everyone else. If you have an enemy so everyone suffers . . . just, ugh. It's fine if everyone gets fallout, but it's bad if you are all equally in the same boat. Or worse, if your enemies attack your fellow PCs instead of you so you are the only one not suffering.
- they give you a free ride, and make the GM do everything. Basically, if Enemy means you get points and the GM just inflicts Wandering Damage on you when they come up, and that's it, it's not really making your character more interesting. It is just offloading roleplaying like it's a chore.
Tuco Benedicto Pacifico Juan Maria Ramirez aka The Rat
Okay, I didn't have any Ugly. But I like Tuco and he's sort-of Blondie's enemy.
Actually, Tuco wants to be a ruthless enemy, and he's certainly ruthless and harder to keep down than the Terminator. But he works out to be an advantage for Blondie. He's a net positive, and provides Blondie with a living, a timely ally, and great chances to show off his skills. He's more like an Ally you have to shoot at sometimes. Or more likely, he's another PC with a really good sense of humor about letting the other PC trick him all the time. :)
In the end, having an Enemy should be just like having Bad Temper or One Eye or a Bad Reputation. It must have an impact on you, and make the options for the character fewer but also drive some play. If it's doing more of the bad than the good, it's probably worth wondering if it's worth allowing.