Streets of Rogue

This ending is unlocked by getting to the final stage, acquiring the hat (by whatever means possible) and then throw it into a hole.

To accomplish this, you should turn on as many mutators as you can to make it as easy as possible. Use the soldier and save his grenades (or pick any class and find and hold on to any grenades you find).

When you get to the last stage, don't give you weapons to the bouncer. Either bribe or fight him off. Now, you can use grenades to destroy the boundary of the level to make a path to a hole at boundary. Once you attain the hat, throw it into the hole. You must do this by opening your inventory and discarding the hat. Just jumping in while wearing it won't do the trick.

Update: It seems you must drop the hat and punch it into a hole to unlock. Possibly changed after an update.

Steps
Purchase Rewards: Giantizer ($7), Kill Healthenizer($10)
Mutators Used: Infinite Ammo, Money Rewards, No Disasters, No Patrolling Cops, Quick Game
Floor: Uptown (5-1)
Character: Custom
- Stats: Endurance 1/4, Speed 1/4, Melee 1/4, Firearms 4/4
- Traits: Bullet Breaker, Blahd Basher, Crepe Crusher, Scientist Slayer
- Starting Items: Machinegun, Kill Healthenizer, Giantizer, Cologne

Obviously you can use any character you like the above is just what I went with. The key here is to have the Giantizer ready for after you obtain the mayor's hat so you can clear the border of the level to get to the drop off point easy and guaranteed.

Mutators are not needed just make things easier especially Quick Game which means you only have to play through 2 levels of Uptown instead of 3 and infinite ammo in my choice so you never run out of bullets and just waste all the bad dudes.

Once on floor 6 I bribed the guards ($240 this varies based off certain factors) to skip any trouble at the front gate.
Then go dispatch the mayor and his goons and pickup the mayor's hat .
Walk to a floor wall edge and pop the Giantizer (open inventory and select Giantizer and press )
Once you are GIANT simply walk through the wall until it opens up to the ledge (black space).
Then back up from the ledge
Open your inventory , select the hat and press to drop it.
Once it is on the ground unequip any weapon (open inventory select active weapon and press and switch to fists, then simply punch it off the ledge.
You will get some story text and then the achievement will pop.


Prerequisites
Elevator Access Unlocked: Uptown
- Alternatively you can play thorugh the entire game
Rewards Unlocked: Giantizer Kill Healthenizer