This game has forced of me to use a good amount of strategy thus far! I've had two in particular that I enjoyed after I figured it out.

My first was against Chapter 4-5ishOdin

(SPOILER)I found Odin particularly tough, there seems to be a consensus to this among my friends. I lost quite a few times before I noticed his attack pattern and how he'd stop attacking for a while after he put up his shield. So I decided that the best way to build up a chain would be to screw trying to attack while he dominated me with his flurry of rape, and whenever he attacked switched my party to a pure Medic one and then when he put up his shield went on an all out offensive. Then he dawned his rape sword again and I cowered in fear as medics again xD Eventually, Ge-whatever mode showed up.

The other was against some flying motorcycle-esc monster in Chapter 7ish.

(SPOILER)He had this attack called "Gattling Gun". It wasn't a very detailed strategy. Just make sure I threw Sentinel on to save Hope but not get a game over by taking the brunt of the attack without defending, once it was powering up. But I felt so proud for using the battle system as they intended!