Put on the rocket boots, jump onto his head, turtle, then cast Black Demon.
He will counter with Black Hole, which ends up killing him instantly.
gaming.stackexchange.com/users/58213/farmer joe
All you need is 2 berserk potions.
Make sure you have about 1872 hp, if not there is time for 1 potion in between berserker potions(have to have about 1000-1200 hp to survive his Hello attack).
Please note that this assumes that you have the double damage item and the unicorn horn.
List of equipment:
Scythe, Pink Gloves, and Normal Knights Armor.
Wait until you reach the developer, as soon as you reach him pop a berserker potion, then wait until his first attack finishes(Hello) and then pop a berserker again.
You should kill the developer just as he drops his second attack on you.
gaming.stackexchange.com/users/58147/Tangy
Drink Turtle potion and when you are near Developer, use Erase magic to insta kill him
gaming.stackexchange.com/users/58272/candyking
Go in with a scythe.
Use turtle potions right before his first and second 'words' hit you.
The third set of words is always fatal, so once the third set of words appear use the black hole spell to finish him off.
Using the black hole spell will cause him to use the spell back at you and kill you, however your black hole will kill him slightly faster and you'll be allowed to keep the spoils.
This may be a bug - it seems that he gets damaged from his own black hole as well.
This method does not require any pain au chocolat upgrades.
If you've missed the black hole spell: You can obtain it from the purple fin off a shark in the undersea area.
You have to go pretty far in to encounter it however - you'll likely need pink gloves and a unicorn horn to sustain the sea snake orb damage long enough.
It won't appear until there's roughly 2 sea snakes and 3 sharks on screen at a time (but much like the other fins, you can't miss it).
gaming.stackexchange.com/users/57993/degs
I found the easiest methed to be walking up to him and casting black hole and immediately teleporting.
You will survive his black hole because of the teleport, while yours kills him.
gaming.stackexchange.com/users/38633/Sharlike
i bought the scythe, put on knight armor, then i just attacked him killed him
i like 5 seconds.
But i had the claw, a unicorn horn and and the rocket boots.
and 200% attack from wishes in the well.
gaming.stackexchange.com/users/27081/Thomas
How I beat him was quite odd...
I used rocket boots to get to his head in that little notch, but I couldn't fly over him.
I had my octopus crown of obsidian on, (the one that summons octopus kings), and I equipped my scythe and enchanted knight armor.
Once I was on his head, I used my obsidian wall spell and won almost instantly...
he didn't even get to use his 'Hello' attack on me.
I don't know if it will work for you.
I'm still confused about it, but I got my 'L' stone
and I'm happy.
gaming.stackexchange.com/users/65112/canadia-girl
The third attack seems always fatal.
The only way I could do it was to kill him as quickly as possible.
The trick was to equip the knight body armor instead of the enchanted knight body armor, as this does damage much faster.
I was using the scythe, the octopus king crown with jaspers, and had power upgraded to 60% more (by throwing pains au chocolate into the well).
I used one turtle during the second attack.
gaming.stackexchange.com/users/5622/shipshape
Wear the normal knight's armor and not the enchanted.
Don't use any spells, and use a berserk potion and a turtle when his first 2 sets of words form.
He dies quickly that way.
gaming.stackexchange.com/users/58200/user58200
I killed him by using the scythe 1 cloning pot and 2 turtle potions.
I used cloning potion at the start and turtle potion on the first word hit and 1 on the second words hit.
And he died while the second words were hitting me.
gaming.stackexchange.com/users/58331/BSA101
I used the giant spoon of doom,(damage increase from gift at well: 1000% more powerful, used pains au chocolat).
rushed him.
Had about 5040 health at the time.(from gifts at well using pains au chocolat)
Use Knights armor(non-enchanted), Pink gloves, Octopus crown with jaspers in it, and regular leather boots.
at the minute when the first words go to hit you, use erase magic.
You should win.
I did.
In case you don't have it:
The advanced grimoire is obtained from the sorceress' hut.
It is bought from her, for how much I can't remember.
but It tells you.
It does cost quite a bit of lollipops, so get a lot before going to buy it.
I think more than 200,000 would do it.
probably more, excuse me if im wrong.
ps:
Please excuse the need for a stupid amount of pains au chocolat.
he asked how to beat the developer, so I told him how I did it.
pss:
Hope it works!!
gaming.stackexchange.com/users/58449/Black Rain
Use erase magic, it instantly KO'd him for me.
I got the stone before dying.
gaming.stackexchange.com/users/65343/snowyz
What I did was equip the Scythe,
Octopus King Crown with Jaspers, Normal knight body armor, Pink enchanted gloves, and rocket boots.
I also had 2180 health, the red shark fin, heart plug, heart pendant, unicorn horn, and the Xinopherydon claw which gave me +60% damage and +40 health.
I ran up and didn't use any magic, just focused on killing him as quick as possible.
gaming.stackexchange.com/users/228080/Big Tasty
I used clone and berserk potion, and he fell like a sack of potatoes
gaming.stackexchange.com/users/58137/Pwnz
Wait until you climb on him so that he will touch himself with his uber black hole.
Cast your own blackhole and immediately teleport (use the keyboard shortcuts, you can also slow down time if you have difficulties).
Ideally you wouldn't take any damage at all and earn 5m candy in about five seconds.
gaming.stackexchange.com/users/58251/John Smith
How should I kill the developer? I have tried this method: jump onto his head, turtle, then cast Black Demon. He counters with Black Hole, which ends up killing me instantly no matter where i am
How do I kill the updated Developer?
gaming.stackexchange.com
<candy-box-2>
gaming.stackexchange.com/questions/137143
gaming.stackexchange.com/users/58013/Candyman
You can drink a turtle potion or a berserk potion, walk up to him and cast a black hole and teleport.  It is adviced to use specific tactics and items, in order to kill the Developer.
Few tactics are listed.