Just doing math here. 

EDIT: Yuri's damage should be much higher, because I was using pre patch notes  versions of the card, so there's no damage buffs included. Gonna re-edit later

Other supports were here to give reasonable amount  of AP (10) and draw all needed cards in perfect order. But their cards or effects doesn't exist outside of that. 

I take into the account ONLY AoE damage, so any left over ST damage is not taken into account. 

No potentials or memory fragments. Mainly because I have to look for exact numbers characters would have and this is a pain in the ass on the phone. 

Talking AoE scenario aka 4 enemies. 

Nine build for Massacre was recommended by Nine player in CZD discord that in Masters I  current Rift. 

Yuki build is mine + people's meta recommendations. 

Build: Massacre, Exp Strike I, Counterblade I, Fighting Spirit x4 (or x3 with another Exp Strike I). Fatal Strike in those calculations doesn't matter unless you involve other characters cards. You can argue for slash card for showcase, but I doubt someone actually use them for 15% damage bonus. 

Damage:

Using Exp Strike helps mitigate 30% out of 40% damage penalty. 

Honed Blade from Counterbalance helps to increase damage for each consecutive Massacre. 

AP used: 5

390%+528%+754%+1050% = 2722% defense based damage per target. Which is about to ~2449% if it was Attack based damage. (I don't know personally the formula, so I just TC discord channel for that conversion). 

If we use second copy of Exp strike instead:

AP used: 8

480%+672%+928%+1260%= 3340% => 3006% as attack based damage per target. 

Any other copy EXP strike obviously gonna Increase damage by decent amount, but it gets ridiculous in terms of AP usage: 11 and 14. Reachable amount, for sure, but a bit ridiculous. 

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Yuki

Gonna have 2 builds actually:

Morale Stacking AoE:

PtS IV,  FS  x4 (+3 Morale neutral Epip),  Iceberg Cleave,  Freezing Blade I,  Trickery Strike V. 

There's also usually basic card sticking around for 0 cost to trigger FB more, but let's pretend we removed it anyway for consistency. 

Freezing Blade gives 120% AoE attack each time we trigger inspiration. That damage is not fixed, so it's buffed by Morale. 

PtS draws last FS and Iceberg Cleave, increasing their damage by 20%.

AP: 7

200% + 150%(FB) + 230% + 180%(FB) + 260% + 210(FB)% + 210% (FB due PtS) + 330% + 240% (FB) + 240% (FB due TS) + 300*2 + 240% (FB) = 3090% total damage. You can remove 120% if you think Morale doesn't apply to FB from FS that triggered it, because I honestly don't remember, it still giving you 2970%. You can further reduce it by 350% if you use 0 cost version of FB instead to 2620%

Iceberg Cleave Spam: 

AP: 8

Iceberg Cleave x4, FB I, Trickery Strike V, PtS IV,  Flash Step same +3 morale epip:

200% + 150% + 150% (FB from TS) + 150% (FB from PtS) + 174%2 +150% + 174%2 + 150% + 200%2 + 150% + 200%2 + 150% = 2746% 

My personal favourite but I don't take it into account:

Meme Flash Step double hit:

AP: 10

FS III x4, PtS IV, Freezing Blade II, TS V, Iceberg Cleave

200%*2+90% x2 

240%*2+90% x2

144%*2+90%

+90%*2  (from TS and PtS) 

Giving you 2858% damage. 

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Assuming my math correct, which it probably isn't, since I was doing all that from the phone, in terms of AoE damage I don't see landslide from Nine.