As far as I know the game by default isn't too friendly with 1920/1080 in fullscreen because of the way the developers programmed the game. However, there is a guy working on an enhancement mod called Pretty Prinny that's supposed to help add more resolution options among other enhancements. At this point the mod is mainly targeted towards the original Disgaea PC, however, I believe the mod developer stated that it is compatible with Disgaea 2 and Phantom Brave since they run on the same game engine. If it isn't fully compatible right now I'm sure the mod developer will add compatibility in due time. If you're interested here's a link, the latest one is version v0.7.x.

https://steamhost.cn/steamcommunity_com/groups/SpecialK_Mods/discussions/9/2741975115064735841/?ctp=4

thank you mafoo, i will check it out.

I checked and now i have full hd without bars(like in window mode)i hope they will add 4k support soon, thank you.