Probably my favorite boss in the whole game, Absolutely awesome aesthetic, sound design (The sound of his lightning nuke and the way it cuts out the music is just... orgasmically badass) and spectacle, very deadly but well-telegraphed and fair attacks, doesn't pull any cheap tricks or bs one-shot attacks/comboes and gives you plenty of good openings to hit him provided you correctly dodge his attacks, amazing music, amazing very spacious arena and great atmosphere, , Easily the best boss imo

Just goes to show you that the game WILL give you the tools to greatly lower the difficulty on a fight you think is impossible. Just like spamming swarm of flies at Malenia makes you question the whole "hardest boss ever" idea, using Maliketh's Black BLade AOW on Placi while a spirit summon distracts him can actually 1 phase kill this guy. I know the naked w/a club RL1 guys will say it's cheap and you ruined the game but you know what guys, the game is not "meant to be hard" it's meant to sell 20 million copies and make a ton of money. If people need a way through let 'em have it.

TL;DR If you are struggling with this boss but want the Remembrance or need to use the needle then grab the Black Blade and you can practically eat a snack while watching him die a quick, cheese-filled death. Eat some pizza rolls for the irony.

So when he’s low health and he does that flying electric swipe, you want to start running close to him if he is using his fire breath, because that means he will use the laser beams, and you can use this moment to get behind him and basically it will be free dmg, I also recommend using black blade incantation and the maliketh’s black blade, it will melt him.

that sheer amount of follow ups he has beats any other boss in the game, including Commander Niall.

This dude and the Fire Giant are the only bosses that legit whooped me for 2 days each. First play-through, first Souls-type game, and I finally got the resistance I was looking for. Nice.

I was previously Str/Fai, but doing Int builds now with only the Str/Dex/Arc needed for weapons I like. 45/35/25 for Vigor/Mind/Endurance. I got desperate and popped every talisman I could to get the Str/Fai requirements for Maliketh's Black Blade. Got him down to 1/4 many times, tried different spirit ashes, weapons, AoWs. Nothing! This page recommended the Death Poker and that was the answer. Used the Lion Bow with Radahn's Rain AoW + Radahn Spears to get to Phase 2 quickly. Also, make sure you dodge/roll toward him and slightly to the right when he does his peek-a-boo move to skydive on you. Keep moving and don't sprint unless you see Red Lightning at your feet. Save the Stamina. Run away when he starts charging AoE bombs. My Mimic Tear and I MELTED him in Phase 2 with Death Poker's AoW at the base of his tail just behind his leg. That's one hell of a stick! Other than that, I equipped the Fire Prelate Chest Armor for the stats. Definitely helped. Boltdrake +1, Flamedrake +2, and nothing else special. No Rune Arc, food, grease, etc.

he stole the place in my heart away from midir lol

Lucked into a cheese for this boss after numerous attempts where I would get him down to ~20% health and then get one-shotted by his laser attack or teleport *******.

Walk forward to a bit before the circle of pillars, and summon Latenna.
While staying the same distance from the boss, move a decent distance away from Latenna, otherwise she will be collateral damage when the lightning attacks start. However don't go too far or she will despawn.
Now keep walking forward until Flaccidosack's health bar appears.
When it does, lock on and start walking to one side (doesn't matter which direction).
Whenever you start to see the red lightning appear around your character, dodge roll 2-3 times to avoid being damaged. Then start walking in the other direction. Rinse and repeat.
Flaccy will sit in the middle of the arena for the entire fight, roaring menacingly, while these easily dodgeable red lightning AoEs periodically appear at your feet. He will never attack you or Latenna. Latenna will plink him to death and you will take zero damage.

Something allows you to warp directly to his arena to fight him from the map screen. I have no idea what. I made it happen on my first playthrough, somehow.

Black Blade, and Maliketh’s Black Blade work WONDERS against him.

Might be the only enemy in the game where "cheese the lock-on mechanic" is a thing.