Chapter 24 wasn't so hard for me as I did a lot of grinding on my characters and maxed most stats with Limit Breaker. However in Lunatic normal it was a huge pain as I did little grinding and my best unit was Noire with Vantage + Vengeance. Anyway I've beaten Grima with Avatar/Cordelia and Morgan/Severa (all equipped with brave tomes/weapons) :D