Warmonger medal not unlocking

Make sure you've done each individual chapter - including the prologue. Have you beat the game on Insane yet? If not, you can check by seeing which chapters have the Insane "icon" on them. Check which one doesn't, and complete that one.

Cheers 

Thanks.  I am checking/redoing all prologues.  I have completed on insane, 4 red stars on all chapters.  I'm now gonna keep a log and replay all chapters on all difficulties.  Eventually it will unlock. Keeping a log is the only way to be sure! Got alot of campaigning to do for those precious Onyx medals!

you have to do it in arcade, and I've also read some replies on the net saying this one only unlocks if you do them all in coop.... I can't confirm cuz I haven't done it yet.

I had a similar problem, did them all on hardcore but my medal only unlocked at casual level, even though when I look at chapter selection it shows all acts at hardcore level. I did however replay a couple of chapters at casual, so not sure if its just taking the last difficulty of each chapter. Going to replay those chapters on hardcore tonight and see if that works

My onyx medal is not unlocking and its driving me crazy.I beat everything on insane plus 4 player co op but no medal Im a try and play this backwards and if that dont work epic needs to fix this since alot of people encountered this glitch.

If I'm, not mistaken, you need to complete all chapters of Arcade on Casual first.

You are mistaken

The warmonger medal does say complete every arcade chapter on casual

if u didn't get the medal try playing and beating the last level on the setting you want. This worked for me when I beat the game on insane but didn't get the medal for normal campaign.