Gunnthra's best team mate?

Arvis is great in a mixed team. For me, Xander is a excellent option, both are cavaliers so they can buff each other and Xander with the distant def build he now can reach 41 res on enemy fase!

Arvis, Lute, triple threat Shareena... Anyone that can debuff.

Xander has been working well for me. TA QR Bonfire and cav buffs really help.

I was planning to do that. Don't forget a Dagger unit with a refined Smoke Dagger+. With these debuffs Gunnthrá hits like a truck.

What about sigurd with his speed smoke and then attack smoke SS? Can he gel with Gunnthra?

Lute!!!!!!!!!!!!!! Lute has higher res than Arvis to debuff stats, AND she can kill the reds for Gunnthra! Also daggers like Jaffar, Kagero, and Saizo help a lot.

I guess just anyone who can debuff.
So obviously Arvis and dagger users, even though I feel Gunnthrá has enough debuff potential as is (she already lowers the enemy's Atk, Spd and Res provided she is over 50% HP and gains 22 dmg as Res counts twice), she just needs a Def debuffer to gain 5 additional damage. Her best allies might actually be normal buffers for bladetomes with a Def ploy or threaten Def I think.