Units: Any unit with good range, high defense, and good melee.
Items: Cyclops (Optional)
Note: All units have the "S" and the end of their rank, so the list goes:
Devil Gundam (aided with Master Gundam in Hyper Mode)
Phase 1 - The first MF you fight is Gundam Rose (Super Mode). He won't really charge at you because he relies on his Rose Bits. After half his HP is gone, he will go into Super Mode. He will then rely on melee attacks and his combos.
Phase 2 - Next up is Gundam Maxter (Boxer Mode). He will rely on all of his melee attacks. Again drain his health to halfway, then he goes into Boxer Mode. Just be careful and evasive against him because his melee range is great.
Phase 3 - The Bolt Gundam (Super Mode) is the most defensive one. He will charge at you but at a slower speed. Again, drain his health then he will go into Super Mode. Be careful when fighting his Super Mode because he has the Graviton Hammer (works like Hyper Hammer).
Phase 4 - Nobel Gundam (Berserker Mode) is the easiest one here because she is a BS Rank and has the smallest amount of health (other than Rising Gundam). But it has the greatest melee range in Normal mode, because of its beam ribbon. In Berserker Mode, she will first charge at you with the Dash Attack, inflicting Bullet Zero. The only hard part is the Gundam Heads, as they will stun you and after you kill one, another instantly spawns.
Phase 5 - Dragon Gundam (Super Mode)'s first attack is the Flamethrower (short range), so he's vulnerable for a few seconds. Then, he will attack you with great melee speed. In Super Mode, he will attack you with a combo move and just keep charging at you, so be quick and have a lot of boost.
Phase 6 - Gundam Spiegel (Messergrantz) is not hard until you drain his HP to halfway. He will go into German Ninjitsu mode and will be able to become invisible. Rising Gundam (Repair Kit) will also appear to give him HP, so destroy Rising first (you get an HP bonus for doing so). After destroying Rising Gundam, destroy Gundam Spiegel, and be very evasive because once invisible, he will attack you from anywhere.
Final Phase - There's a rock for a reason: To avoid Devil Gundam's attacks. At first, he may seem pretty easy until a certain amount of his health is gone, then he will have a barrier. To make it more dangerous, Master Gundam comes to Devil Gundam's aid and tries to kill you. To destroy the barrier, destroy all Gundam Heads in the area and continue shooting. The barrier will reappear at certain times, so be careful not to waste your ammo a lot and at the same time, be evasive.
There you have MY perspective of completing this mission. If you have any other ways to beat this mission, leave em in the comments :)