Sep 07 2009
1. Well-constructed characters generally do not need weaknesses. If you have to resort to something like a vulnerability to Kryptonite or the color yellow or whatever, it’s probably because the character is too powerful to begin with. Something like Kryptonite is not a satisfying or particularly effective way to resolve that. For one thing, going from “largely unchallengeable” to “helpless rag-doll” does not make for great fight scenes. Also, relying on Kryptonite may force writers to pull goofy Kryptonite Ex Machinas where minor criminals somehow acquire rare and random substances.*
*Some Superman stories explain this by having Lex Luthor give Kryptonite out to criminal groups, but it’s incredibly rare. Why would a random gang have a better chance of killing Superman than his own assassins?
2. Kryptonite-style weaknesses are a bit outdated. In the past twenty or thirty years, there haven’t been many major superheroes that have been successfully introduced with a serious vulnerability to something that’s usually harmless.
3. Rather than using something like Kryptonite to limit your protagonist, I’d recommend limiting his capabilities instead. If the character is practically indestructible and can move as fast as a space shuttle, then you practically have to pull something like Kryptonite out of a hat whenever you want to challenge him. But the fight scenes are generally more interesting and the character will probably be more relatable if his powers are less impressive to begin with. Over the past thirty years, heroes that are merely somewhat better-than-human (like Wolverine, Batman and Spiderman) have been dominant. Heroes that are so impervious that they need a gimmick weakness have generally not fared as well.
3.1. Another approach would be making the character’s opposition more powerful. As long as the character can be challenged, it’s not a cosmic disaster if he’s essentially a demigod. (That said, unusually powerful characters do raise some obstacles for writers — for example, if you’re writing a character like Batman, you can write interesting scenes with unpowered criminals, but a character like Superman basically forces you to pull out supervillains if you want to do anything. Supervillains usually require more thought/preparation/attention than an unpowered mook would).
4. If you’re deadset on using a vulnerability, I’d recommend using something that is usually dangerous. For example, the Martian Manhunter has sometimes been vulnerable to fire. That is a lot less goofy than the Green Lantern’s one-time vulnerability to the color yellow or wood. Alternately, if you’d like to try something creative, I’d recommend looking at things that are plausibly dangerous for someone with his powers. For example, someone with particularly good hearing might be sensitive to loud sounds. Someone with psychic abilities might be vulnerable to anything that disrupts his concentration.
5. If you’re deadset on using a Kryptonite-style weakness, I’d recommend having it be merely damaging rather than incapacitating. As noted above, if the protagonist is limping around like a rag doll after getting poisoned by Kryptonite, that really limits your opportunities for fight scenes and other interesting sequences. One alternative would be having the weakness temporarily disable the character’s powers. The character would still be very vulnerable without his powers, but at least he’d be able to try to do something. (For example, you might have him fight an unpowered battle against low-level mooks or do an escape scene where he tries to get away from a superpowered villain that is far too tough for him at the moment).