It doesn't hurt at all. If the achievements are buggy people will complain about it either way. The devs aren't looking at the percentagem and saying "oh! One guy unlocked it, so there's no problemas!" Thats not how it works.no, you don't know anything about it and your words are just that words, like mine, deal?
All in one second? Don't make me laugh, at least most people don't care enough to hide that they cheat.
It does hurt, you should try to prove to dev that achievements are buggy when obviously people get them.
And did you seriously check every single one of those TF2 achievements to see if they were all unlocked in the same second? Like, do you do this all the time?
Also, nah, my words are more reasonable.