Any reccomendation to beat hassan's parade?

You have a few options that should work fine. I'd either use Medea Lily + Medea + a borrowed Da Vinci (or other caster aoe DPS that has the White Rose CE), or I'd use Medea Lily + Tamamo + a borrowed Amakusa Shirou.

If you use the first option, you might need to give Medea like 10-20 levels, but that might not be necessary. Just use her NP against each boss Hassan to remove the buff, and then use the borrowed DPS to kill it. You could also use Tamamo instead of Medea Lily, but Medea Lily's debuff clear would be really nice for this.

Personally, what I did was use Tamamo, Waver, (friend) Amakusa, and Irisviel (as back up). Im thinking you’d probably want Tamamo, Medea Lily, and Amakusa at the start. You could possibly switch Medea for Irisviel, but that’s up to you to make that call.

Just try to keep Amakusa up through the whole thing. You need him to the end basically to remove those insta death debuffs.

I’m not sure what I’m saying will help, but this is the strat I used and it worked. So I hope something similar will work for you as well

You have a solid team. I didn't have even close to that good of a team and I was able to do it, but it does take the slow and steady approach. 62 turns for me.

I used Medea (lv 40), Hans, and Mash. That's it. Just slowly kept building np, defending, healing, etc.

You should use Medea, Medea Lily, and Mash. That will carry you for sure if you just take it nice and slow.

I think you have all you need to beat them Hassans' (feel a little bad about blasting Serenity though)

Got through the stage just fine with Medea, Helena (Main Attacker) and Casko. Helena doesn't even need an MLB'd White Rose, not one of them went down so back-line wasn't even needed.

Medea is crucial for dealing with the four boss Hassans with the death gimmick but you'll have no problem with that since Tamamo can heal her and to a lesser extent, Medea herself (She can also take away those annoying debuffs from your Main Attacker). Just level Medea more but don't stick any CE's that will boost her damage so she wont accidentally kill any of the Hassans with the death gimmick when her NP hits.

For your main, Nitocris will do just fine. Levelling her first wouldn't hut though!

my team was
Helena lvl 60 (event CE)
Medea lvl 50 (event CE)
borrowed Medea Lilly
Medea one shot the first Hassan and lost a life.

I think Nitocris + Medea + Medea Lilly should work

I only used Irisveil, MarieCaster, and Tamamo and it's super easy.

Medea Lilly+ nito + Waver
was my team

Reading all these answers, I seemed to either be doing it wrong or missing something. Medea clears debuffs with her NP, true, but only after damage is done. So I tried using her- first turn, skill 1 for immediate NP, killed Hassan, she died. Seems the debuff works immediate upon death, regardless of her Rule Breaker gimmick. Eventually did it with Iri and Nursery, but what did I miss?

I went through it with Nitocris, Medea and Da Vinci (Support) in the front line. Iris in the back line for healing and guts NP. The key was keeping Medea alive long enough to remove each boss' death buffs with Rule Breaker. Spammed Nito and DV's AoE NP's.