You unlock following achivements (9/19) while beating the game:

Welcome to New Koza

Utopia

Going Down

It's just uhhh...Flour

DESTROY ALL ROBOTS

WanChai Connection

Calamari

Nostrovia!

World Class Wrecking Crew

(Congrats, you beat the game.)

This section with other 5/19 achievements.

If you get stuck, try to farm some level and items(or get skill from Box).

"+ATK (skill) power" weapons/kicks/gears works great with Yazawa's "Schwing!" for farming mobs.
"Elitz" gears give you extra SP & ATK power when battle start, help you both in mobs/boss fight.
You can also let others equip "+EXP gain" weapons makes farming even faster.

Machiko's "Ghetto Blaster" can massively reduce enemy's states, combine with Vanilla's "Deadeye" you can deal massive damage to boss.
If Boss has buffing skill, try use "Fakeout" to dispel their Buff.
And most importantly, Stun/Flame/Freeze helps you win!

Doggy Style



Very soon in the game you will find a dog at Fishbed Town, after taking home and name it.
Whenever player come close it will bark and pop lots of heart <3, just stand there & wait, your doggy will gift you a great stun skill.
Doggy Style helps a lot in boss fight, so player better got 4 for your whole party.

Microtransaction



Player has low chance (5%?) encouter this special enemy instead of normal mobs, it gives GREAT unique weapons and EXP! it always trys to run away! "Doggy Style" stun it first!

Now that was unexpected



After player defeats T2 military robots, the 4th teammate Jackie will join soon, and you have to kill this old man after steal all his money, which make him super strong, nice troll!

Before battle start, let Jackie equip "Elitz" gears so that she can use "10-Step Kill" + "Taunt" combo tank all the attack unharm. Other than that, try stun/flame, "Fakeout" his buff and throw whatever you have at him.

Executive Decision



Early game player will drive to Seaside Drive-in, having meal at a restaurant talking story...
Try walk in kitchen and steal their frozen pizza, and now you are F**ked! lel

However lv62 Chef isn't as strong as it seems, cause "Instant death status effect" works on him!
Ideal unique weapon is "pestigenocide", but any "instant death status effect" weapons do the job.
Try "Doggy Style" stun and shoot him, sooner or later he dies. (Hope grayfax won't patch it)

Negative Drug Test Results



After player reclaim "Smile Bakery", you can revisit the bakery and taste their...flour?
Then you wil encounter 3 seems unkillable harmless green Yakuzas.
Check? "Instant death status effect" again!
The unique weapon "Lil trip" they drop is only good for mobs farming.

The rest 5/19 achievements are here.


After you beat the game, go back where Machiko lived, pay lots of money to start a post-game quest.
Kill "Home-run Senpai"! Most post-game achievement finded here, all mobs are lv60+ In this area, but fear not, if you have good gears you can kill them at lv30+. also, Box Dog can be found here!

(Sadly, "instant death statu effect" doesn't work on most of them...)

Oh, it's just a dog...



Annoying mob, resist many status effect, only weak to electric.
Can be fatal if player too careless, let Jackie "10-Step kill" tank all its attack.
After beating it once, just escape next time you encounter this Dogcopter, then restart the mobs battle to see if you can pick easier mob fight.

Blockbuster



Another annoying mob! Can't hurt player but f**king tank, hard to take down if it start buff itself.
Always try stun this wall first, wipe out its team, "Fakeout" its DEF buff then "Ghetto Blaster" + "Deadeye" nuke it down.

Sempai Slayer



After Exploring both side of the map, player can now enter the secret room to meet your senpai...

It is not too hard to win the boss fight, in my case, I grind my party to max level (60).
"Ghetto Blaster" + "Deadeye" combo in offence.(+ATK gears)
Jackie "10-Step kill" + "Taunt" (Somehow it's not always dodge...) in defence.(with +Def, Elitz gear)

"Night of Fire" for Flamming,
"Flaming troll" (+200%ATK, +100%Crit if target flammed), for Vanilla's "Deadeye".
And always Doggy Style Stun!

The Ultimate, Most Powerful Woman in the Milky Way



After you defeat Homerun Senpai, revisit last area again Evil Chef will replace Senpai.

Now this fight is hard and require RNG.
First turn Chef most likely only buff herself like crazy and less likely to attack.
But if Chef
You better reload the game file.

One of my team equip "-shock resist" weapon to debuff chef at first turn (With "Deep Breath" or bullets won't hit), when second turn start, fakeout her buff.

Then you can only hope all your "Doggy Style" stun landed. (Told you it need RNG)
Per doggy Style stun last 2 turn, so if all your team stun land you have 8 turn of free hit.
Combine "-Stun resist" "Stun" "Flame" + "Flaming troll" I finally beats the Evil Chef.

Update:

Originally posted by Edwin.Deleonx:

You can 2 turn KO the Evil Chef. Let Yazawa equip all the best skill power buff item:

Short gun- long barrel holo cryo lil trip- 100 skill power
kicks- full dope sonic high heeled thunderbolt fortress - 200 skill power when you AP is full
gear- full guard medic ballistic helmet- 200 skill power when AP is full

Skill ability stack up make sure your AP is full so can trigger

In his YT video, Yazawa taunt first then get KO, which makes Yazawa full AP.
Then team revive Yazawa, dispel Evil Chef buff, "Schwing!", OHKO Evil Chef.
(Other teammate also used some weak debuff weapon on Chef, may help)

Thx for the info! You don't even have to use stun to win the secret final boss!

The Abyss of Power




Technically this one isn't post-game, but often you need high level, lots good +ATK gears & weapons to reach 1Mil damage.

I think most player got this achievement with Yazawa's "Schwing!".
Go to Gunshop (mainmap, top floor, bottom right), use "SP max Shooting Range" as dummy target.

Ofc Yazawa equip all the +ATK gears (+skill power or +normal atk power both stack).
Some +ATK gears require set up, like skill reload or need be marked to recived the +ATK buff.
If you don't have utral powerful weapon, try "Jackpot", at 7th turn it gives +777% damage.

Other teammate try stun & freeze targets, which make next attack hit harder.
Then "Ghetto Blaster" + "Schwing!", you should do more than 1mil damage.

P.s.
Anyone know what "Homerun ball" does? you got this odd ball after you defeat Homerun Senpai.

Originally posted by Windonall:

"Homerun ball" is the key item to challenge Evil Chef.If you sold it after defeating Homerun Senpai,you can not find Evil Chef but Homerun Senpai again in the last area.

P.p.s.
It is fine to hate this game, children thug + strong language irritate some people, I get it.
or just poor story telling & game mechanics

But still, I had fun, not regret my money & time. Yo.