We all have seen at least one James Bond movie (or failing that, an Austin Powers movie). We know how it works. No matter how many minions, henchmen, and devious traps the Evil Genius has laid out, the lone superagent with his PP7 get the jump on the whole base, and foil the plot.
Yeah...that's how it happens in real life. That's why the CIA employs thousands of people instead of just one.
In Evil Genius, the cliche of James Bond appears five times. There are five superagents, one from each of the world powers. These superagents don't appear until you reach a certain level of notoriety, but once they do, they can only be eliminated in one unique way for each of them. For instance, you take the typical Bond-girl superagent (complete with bikini, which is the best gear to spy in) and strap her to a plastic surgery table and make her ugly. You can eliminate four of the five agents by in-game actions and missions before the end of the game. The last superagent, however, you can only kill by strapping him to your doomsday rocket and launching it, which is pretty much the end of the game.
So, before you can kill these agents, they wander around, blowing stuff up, killing your minions, and all that do-gooder stuff. The problem is that, even if you "kill" them, they are really only incapacitated. They will recover stats slowly, but soon will rise again to harass you. One of these agents is enough, but it's possible to have all five beating down the doors of your base. Since there's only one way to eliminate them, they are nearly indestructable.
Which leads me to the point of this post: No enemies or units in any game should be indestructible, or have only one way to kill them. I understand many games incorporate tough enemies, and I'm not against that. Let's face it, World of Warcraft is successful partly because the toughest enemies require large, diverse groups of players to defeat. Also, Neverwinter Nights (another of my favorite games) had several bosses that were very difficult to beat unless you did things in a certain order or had certain items. The thing I'll note is, there are multiple strategies for dealing with WOW bosses, and in Neverwinter Nights, you can blunder through the game without a walkthrough or strategy and defeat bosses in many ways. Some are obviously harder (such as not having a cleric when fighting hordes of undead) but they are still do-able.
A good game has enemies that are challenging, but beatable. Bosses especially should push a player to their limits to some extent. It's okay for a player to have to reload a saved game and try to beat a boss a second time. Heck, WOW guilds run in to beat the same boss 20 or more times if they don't succeed the first time. It's all about balance and fun, relative the boss. There shouldn't be only one way to beat any character in a game.
I'll make one caveat here. There are instances, especially in the Final Fantasy game, of boss fights where there is only one way to win. These work only because they are done once or perhaps twice, and they serve to further the plot. This creates a tricky balance, but a boss that's only limitedly defeatable should be an exception, not the rule, and should only be done for further gameplay, storyline, and fun.
Up next, we move away from Evil Genius and on to an older game: Star Wars Rebellion.