How to (make it easier to) beat Heaven's boss

In order to do this without any major problems your party should consist of at least one person with healing skills ( this isn't really needed if you have plenty of items, however I wouldn't recommend it because of how many would be needed), one that applies buffs/debuffs, and one that deals a good bit of damage. A party member I highly recommend is Naoto because of her base and learned moves, she should already have garu/agidyne, she can also learn tetra/makarakarn.
In the long run it doesn't really matter who you choose as long as you set your party right and are comfortable with it.

Another thing I should mention is your level. I was underleveled when I first fought Nametame and got royally destroyed, the base level I would say to start at is level 60+, your party should also be at that level as well.

When your'e fighting Nametame you should have at least some emergency healing items. Multi healing items like Soma's and Macca leaves are a good choice, as the latter can be bought at the shop. Buff items like Super sonics and Assault signals are handy to have in a pinch. All of these (except for the macca leaf) can be found in chests.

Veggies are a great way to recover hp/sp and can even save your life. Since Nametame doesn't have ailment or light/dark moves don't waste your time growing cabbages or eggplants, try growing tomatoes and melons (or you could just farm for beads). And before you ask no, you wont have enough time to grow paprikas, instead acquire personas with red,blue,green,or white wall depending on your parties weaknesses.

Sp can run out extremely fast if you aren't paying attention, Soma's and other certain items can restore your Sp. Nametame can steal a party members Sp, so be sure you conserve it.

Every time I looked for help for Nametame it was only vauge hints like, "Use a persona with lots of reflects". Now that iv'e beaten him I can without a doubt tell you who to use, ABADDON
If you use naoto and two party members with weaknesses to fire and ice (chie and yukiko), Nametame will spam Agidyne and Bufudyne, While not even batting and eye to you. If you can, try fusing it with a persona with null physical, and it will be a breeze.

Nametame has the ability Quad Convergence, which allows him to reduce or increase elemental damage for both himself and your party, take advantage of that as much as you can, if a party member is locked to one element (like Yosuke) and they are disadvantaged, have them focus on support. If Nametame changes the element to one a party member has (even better if two of them do), spam the strongest version of that element you have, this doesn't work with items like pinwheels or firecrackers however. As said earlier Nametame has tricks up his sleave, such as Sp steal, tetra and makara break, his version of dekunda, and a form of charm that you can't get rid of until a certain amount of turns. A way to cheese him for the first part of the fight is spamming tetra/makarakarn on the mc, unlike other bossfights Nametame only gets one move per turn, so having him waste it on getting rid of your magic wall will allow you to last longer.

Near the end of the fight, Nametame will manipulate all of your party members, this is where null phys comes in, depending on your allies skills, you can comepletely negate all the damage you take. Nametame will also only attack you physically during this stage, this will last around 3 to 4 turns, at that point he will spam an almighty move. This is the easiest part, as long as you heal yourself when need be and deal enough damage, his gears will fall apart and he'll come crumbling down onto the marble floor.

I just hope this guide helps out anyone who is (or was) having trouble with Nametame. If you have any suggestions on what I should add or fix comment down below, this is my first guide so it's not too high quality, ill probably make a guide on Shadow Teddie whenever I feel like iv'e got the best strategy for him.

THANKS FOR READING