How do you beat Heracles in Nero Fest?

you gotta kill him 9 times

I used a MLB princess of the white rose on Jalter as my damage dealer, Mash with prisma cosmos CE, and support Waver. Your archer saber would probably work great with this setup since she has an additional defense and arts up skill. just spam defensive skills and lord camelot as much as possible and remember that Heracles revives over and over you can check how many guts revives he has left by holding on the enemy's icon for a few seconds until it shows up.

It's actually posted here in the Site. I pasted the link below. I managed to clear it with Orion, Support Waver, Tamamo no Mae, Tamamo Lancer, Rider Martha and Mash using the Chaldea Combat Uniform. I plowed through the 1st 2 turns with Orion, Waver and Tamamo then substituted Tamamo for Martha to get rid of the Arts Debuff then grit my teeth and occassionally used the Guaranteed Stun to buy time while charging NP. Not ashamed to say I used 2 command spells to replenish their health as well.

https://grandorder.gamepress.gg/return-nero-fest-2018-act-i-twelve-labors

Well if you havent mlb the lottery ce then you are in a slight better chance of gettibg through the mission(due to damage output spread evenly) since I dont exactly have art type servant

I had a fairly easy time with Mash + CuAlter + Support Waver as my line up. I equipped a basic Princess of the White Rose on Cu Alter as my main damage dealer, and I never even removed the arts down debuff.

However, as soon as Mash randomly died after 7 or so kills the stage became significantly harder, so I recommend exchanging Siegfried and Mash in your line up and use her from the start. It's useful to max her skills.

My backline consisted of lvl 80 FSN Cu Chulainn, Altria Archer and Euryale (she's actually really good in this fight as well because of her charm).

For this fight, sustained damage is important. Use mash waver and cu alter altria archer ozymandias and a tank like leonidas, chevalier, or georgios. Use chaldea combat suit.

Is it possible to use Ibaraki's NP to cancel his Guts?

3 Cu can finish Herc not hard, no matter which Cu he is.

Herc can only make 2 hits per round, so Cu's evade is extremely useful.
And he has 12 guts. You need taunt unite until meet Herc then apply Cu tanky team. And you should make good manage of hits since in most cases overkill is not recommended. Like NP-BB for CuAlter, you should calculate how much one NP can deal damage to Herc then dont waste it to excessive damage.

I use medea grailed to 90 with mlb white rose, mash, support waver george, euralye and helena, it was pretty easy just spam np and stall with waver and mash i think that only mash and george die

I used Lvl 65 St. George with my new max limit broken Legion CE, lvl 70 Mash, and lvl 90 Tamamo. I used one command seal to heal George and didn’t loose one hero. Took 135 turns, but the total 100% defense buffs on George who was taunting controlled Hercs damage.

I beat it with this team
Ridertoki 90 with White Rose
Mash 60(pre Camelot) with Kaleidoscope
Raikou 90 from a friend with MLB White Rose
Tamamo Lancer 85 with MLB Summertime Mistress
Herakles 90 with MLB Sumo tournament
Anne/Mary Archer 80 with MLB Dragon Meridian
Code was the basic one lvl 10 because I forgot to change to Battle Uniform.

Beat it fairly easily with no command seals used and losing only Raikou and Mash(due to unlucky crit the turn before the invuln taunt combo came off cd). On the plus side, that brought in my own Heracles to completely wreck that pretender with a Buster Brave Chain for the kill.

Herc starts off with a multi guts buff to imitate his "God's Hand" ability from the anime. So you have to kill him 12 or 13 times. On the plus side, unlike the anime, he's not immune to the things that killed him, nor does he revive at full health. On the downside, half of his hp bar is still rather big for his attack. So, it's not impossible, just really hard. Either focus on a stun team or an evade team if you have strong enough servants and a powerful support servant.

You should use the MLB Princess of the White Rose CE (+200% Attack) and build your team around 1 main damage dealer + supports as Heracles has 12 lives (11 guts with 50% HP), it's more important you have enough sustain through taunt, walls and healers.

It took me 25 turns with an arts crit team built around a lvl 70 Chloe! Borrowed a friend's lvl 100 Waver with a 2030 CE and brought my own team with lvl 55 Georgios, lvl 65 Hans, lvl 60 Mash and lvl 68 Cu Lancer!

I got super lucky with Cu Alter as Herc kept attacking def buffed Mashu. Cu could OHKO 1 Herc life and when it came down to 1v1, Cu managed to live by getting evade and NP just in time.

Its possible. Used mash lv 60, Squirtle lv80, jalter lv 90 (support), waver lv80 and chloe lv 80. Jalter did all the work. Keep her alive and increase her attack. Waver supports the whole team. Mash uses taunt and invincibility when herc uses NP. Squirtle and chloe were used to finish the last 2 lives of Herc.