Tips for fighting Gawain

Euryale with her 3rd skill maxed (or lv6) is fine
You can try use Matahari if you want to charm lock that Gorilla

If you have her, Chloe is also great to bring.

Hello.

Euryale is good because of not just double charm (skill and in the NP), but also because her Vampirism (good chance of drain Gawain NP bar at least once, charge herself a bi even if it fails), and most important, immense overcharge NP effect that causes a lot of extra dmg to males (specially sabers and berserkers, because class affinity, and specially, the bigger the overcharge).

I would recomend at absolute minimun lv 60, and then last ascension, to unlock her 3rd skill, who gives 20-30% arts up to herself for 3 turns. Then give her some Attack/NP dmg up CE like Golden Sumo/Halloween Princess/Holy Night Supper (different buffs stack multiplicatively with one another), and her NP will be scary if put on 3rd in a NP chain (even 2nd can be enough). Also, at least 6/6/6 skills, if you can afford yellow gems and Dragon Scales.

As for other units:

-David 2nd skill has AOE Evade (for 1 strike), so, it can save you from the Onslaugh of Excalibur Galatine at least once.
Also, do put a Holy Shroud Maddalene/MLB Iron Wlled Training on him, those combine with his first skill will make Gawain dmg be almost negligible on him.

-Waver/Zhuge NP does remove one level of his NP, imposes def down, and has a chance of stun, clearly very good. Also, he can charge someone up to 50% NP bar and another 2 by 20%, plus nice dmg and deffense buffs to keep you alive.

-Robin overcharge effect is almost the same as Euryale, but sometimes Gawain (and others with Magical Resistance) will resist his poison, rendering the overcharge usage irrelevant. He also has an (tied to ST quest) Evade who gives 10 to 20 stars after activaded.

-Orion has a anti-male dmg up skill for 1 turn, an Evade+crit up, and her NP has chances of removing a bar of NP.

-Chloe NP5 with MLB Halloween Princess and her 3rd skill on 10, to damage him a lot.

Also, use Chaldea Combat Mystic Code, to save up your best dmg dealer once from that Galatine, if he can dodge that. And Stun him, delaying Galatine turn.

ps: Be prepared for Mordred, she spams AOE NP every turn...also, use Sabers against Tristan- he has affinities reversed as his gimmick- and Avenger on Lancelot -his gimmick is being a pseudo-ruler.

I use Orion Chloe and Jeanne

You can add me for support Orion. She work well with male boss.

216,028,069

I highly recommend bringing support tamamo along. She will help you cycle through the np and skills to lock down gawain. Also, bring a second arts dps with a charm or np drain. Hassan of serenity can work. Due to how tamamo works, I would say have euryale at lv70 with 666 on her skills.