Most fun killer?

It's really all about testing various Killers and perks, and finding what works for you. There are a lot of "meta" builds and Killers, a thousand tier lists of who's the "best" and the "worst", but none of that really matters. At the end of the day, it's not really a win unless you're having fun.

I, personally, enjoy playing as Doc, Legion, Myers, and Demo.

The Doctor's "Order" addons are super fun - there's nothing more satisfying than seeing a Survivor trying to get your attention in what they think is a safe loop, only to have their pallet disappear as they approach. He's also great with the perk Surveillance, telling you just where to use his Static Blast, as well as Iron Maiden for those who think they can avoid your power.

I find Legion fun as it kinda lets you take on the role of what is basically a Survivor with a knife - you fast vault windows and pallets, you run fast, and you stab people. Since Feral Frenzy attacks don't count as basic attacks, it also works really well with perks such as Dark Devotion and Franklin's Demise. Nurse's Calling is also a safe bet, as they will be healing quite a lot. And there's something very fun about slaughtering a group of adult men as a pink-haired teenage girl with a knife.

Good ol' Myers has a lot of cool add-ons, allowing you to play him in just about any way you want. You can go for an unstoppable beast of a man with Spirit Fury + Enduring and M&A + Infectious Fright, or you can grab an indoor map offering and scare the crap out of people with Scratched Mirror. Either way, the combination of stealth and power is always quite fun.

Finally, there's the Demogorgon. The teleportation thing is cool, but the Shred attack is even better, allowing you to work around perks like STBFL and Dark Devotion. I'm a big fan of STBFL, Mad Grit, and Rancor - hit fast, spam attack bodyblockers, and get yourself a yummy snack at the end of the game. Of course, the most important part is that the Demogorgon is so goddamn CUTE. I don't understand how people find it scary. It's just a big hairless puppy.

Well, that's all for my novel comment - best of luck to you in your future killing sprees! 💚

TL;DR: test things, have fun, and pet eldritch horrors

Huntress imo is one of the best to have fun with, she is balanced and rewarding. Another good pick would be Blight and the Demogorgon.

For me most fun always was Huntress. You need to learn to play her though.

And recently I had a lot of fun with Nemesis using only his tentacle strike. Once you learn how to hit tentacle effectively you become unstoppable pallet breaking machine that devastating at short wall loops and pretty good at high wall loops as well. Bonus fun points when survivors accidently get hits by zombie. You can't seriousluy rely on zombies but when they help it's so much fun.