Most important piece of this fight is the positioning of your team. Keep your team evenly spread across the grid to reduce the possibility of one attack knocking your entire team out. In the beginning, when Morgan Freeman is about to use his fart attack, interrupt it with the Timefart Summon. Not only does this cancel his powerful move, but also calls in a younger version of yourself to assist in the battle.
Use your knockback abilities to try and keep Morgan Freeman centered in the grid, keeping his distance from all party members. After some time, Morgan Freeman will use a Summon Timefart to bring forth one of his own younger selves like you had before. Shift your attention to the younger Morgan Freeman and get him out of the way ASAP.
Once younger Morgan Freeman is down, Morgan himself will start to try and charm your party. Use burning or bleeding damages to deplete his health while you spend your turns focusing on healing your heroes. This final phase will be hectic after your party members start to become Charmed, just try and keep your cool, while using health and revive items when needed.
Survive that final phase and you have officially defeated Morgan Freeman. Bask in your own glory as you have bested the strongest enemy in the game.