The Spectrum of Suvian Species will probably be of at least some help, as it's got a collection of the basic Sue-types and their relative levels of potential power. It's got an odd way of organizing its information, though. For example, it claims that any Gary Stu is inherently more powerful than a Sue-wraith, when that is most certainly not the case, and conflates some Suvian archetypes with power levels, which would imply that any Sue in that archetype shares that power level, when that is also not the case.

Either way, it could work at least as a relative list and scale. Plus, that second link takes you to a list of higher-order wraiths, in case you needed more species of badfic nasties to throw around. Higher-order wraiths are nasty creatures, though, and tend to serve their own purposes more than anyone else's, so if you want to include some, use them sparingly.

...that none of your pillows are bads in disguise.