Slitherine

http://i.imgur.com/ht6Z3rf.jpg
i destroy trapped destroyer but cant earn this i try it 2-3 times

Did you attack the destroyer with your ground unit to force it to scuttle?

i destroy it with navy then cap it with land forces

Many of the achievements appear to be bugged. While playing US Corps, I was rewarded with a bunch of achievements I certainly did not deserve (e.g., Lonely Wolf, Denied Artillery).