Cleared: Metal Slug 6 Trophy in Metal Slug Anthology

All you have to do to get this trophy is finish the game in general. It does not have any difficulty/continue restrictions attached to it, so I'd suggest using EASY/FREE PLAY settings. Also, when you start your game, select EASY mode in game as well and it will make the run a little less difficult and eliminate the final mission, so less you have to beat the game. After you defeat the final boss, the trophy will pop!