I really don't like the Achievements that are based on BKR ratings - for example, the one for the ponds to increase your BKR when you finish 10th or worse. Well that would be impossible for me to do since I already have a good pond rating. Anything out of the top 5 or so will result in my losing ratings points - I would basically have to lose on purpose a few times to drop my rating just to try to get that one..... and even though some will do that, I don't think it is in the spirit of the game site to lose on purpose just so you can then achieve an achievement.
So any achievement which might lead to people to lose on purpose so they can achieve something should not be an achievement.
I know a goal that I'm personally trying for (and screwed myself out of when I at one time started to play a lot of games I don't like when I was trying to get a rating in every game) - is if a person has a 66.66666% win rate (after 1000 played games) - meaning they win 2 our of every 3 games.