-This will take about an hour and a half to complete so be ready for that.

-This strategy isn't guaranteed to work the first time and may take up to three tries like it did when I tried it, but worry not you'll get to that sweet sweet 250k at some point... even if its 4:30AM on a Sunday...

-I've only done this as the wizard and, while I heavily speculate it does, cannot ensure it works without them.

-Time time time... and determination. This took me way longer to complete than I thought it was simply from messing up a couple times over so be ready for that, you might get lucky and get the first time but just be ready for that.

-The wizard... while the DLC is by no means required it is heavily recommended, and hey it never hurts to support your indie devs. This is primarily for the healing spell you get as opposed to the extra weapon to back-kick some of the damage you'll take.

-I recommend having your own music to listen to as well, I would've gone insane getting this if I had to listen to the same sounds of the game over and over again for almost 2 hours.

That's right, every gamers favorite thing, grinding. What did you expect the achievement to boil down to?
You're gonna want to play the game normally until you get to the tree boss shown in the picture provided that I took when I was overly excited at getting to 100k
From here you just, kill the green slimes for a good couple hours until you get to your desired score, the hard part is to make sure NOT to hit the tree, while grinding its children for those sweet sweet points is easy, vampire bats in the final stage aren't, those guys will destroy you when you're at 239k and make you do this whole thing over again.
But its just as simple as killing slimes and not dying, which if you play as the wizard isn't very hard. The boss levels, or at least this one, seem to like to consistently give you at least one of each item, meaning you should always have a heal and something to attack with, the big thing is to NOT kill the tree until you've meet the score you want.


(This image is really low quality for some reason, it's the tree boss, you know the boss that is a tree. Shouldn't be that hard to identify.)
https://steamuserimages-a.akamaihd.net/ugc/1026204128949093454/ED0F445DC112C9126B7BA42624639C031480A916/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false

-The poison of the green slimes lasts for 18 damage, leaving you at 82 health off 100.

-All healing items, hearts or spells, heal for 25 hearts. If using healing spells it is recommended to use immediately after a slimes poison wears off

-The tree will spawn a max of 3 slimes at a time, so don't expect to have to face more than that at some time.

-You can cross the single block of slime at the top and only take about 3-5 damage. This applies for all the slime surrounding the tree but it isn't recommended to cross outside the circled area (see picture for visual)

https://steamuserimages-a.akamaihd.net/ugc/1026204128949092430/5E7D5BC274727AFAB02D016538E4E7AC7222EAE8/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false