If a decent bloke ends up with a monster then he has co-dependency issues.. same as if a decent woman ends up with a monster.
The only decent people who end up with other decent people are the ones who dont have emotional issues and know when to walk away. Even if they really love someone-they will still walk away if/when that relationship becomes unhealthy or dysfunctional..
People who can walk away even if it hurts have very high self esteem and a good sense of self worth and they know what they want/dont want.
Healthy people attract other healthy people in general.
So if you do have issues-any sort of issues from insecurity, low self esteem, abandonment issues to trust issues, co-dependency etc you should be alone and work on those issues if you dont want to attract the wrong type
"Don't ask a question if you can't handle the answer".