Originally Posted by a tiny spider

Okay, this will be my second six star unit, so I've been digging through the wikia to try and narrow my selection down, but nutaku fkg stats don't seem to match up to the wiki consistently.
My Nerine at least lists worse bonuses than the wiki credits it with.

So opinions please -

Lycoris - She's fragile, but her bloomed abilities support evasion tanking and she can give an impressive 67% boost to attack damage party-wide against regular groups of enemies, but only gives a 37% boost against singular enemies and bosses. Her 1.2x skill activation is always welcome. Gorgeous art is a bonus.

Black Baccara - She has impressive, well rounded... stats. Bloomed, she gives a 22% defense boost to the entire party. She also gives a 75% damage boost to two party members, as well as 10% to the remaining members for an average 36% boost. Her 1.2x skill activation is always welcome. Gorgeous art is a bonus.

Saffron - Impressively high stats. Bloomed, she gives a whopping 30% defensive boost to the party but only a 22% damage boost. Piling evasion tanking onto regular tanking makes her easily the most durable six star FKG, with the caveat that her high evasiveness makes her powerful defensive counter less active at dishing out damage. A demerit - no skill activation bonus.

Helenium - Sturdy, she skips the evasion and goes straight for the kneecaps. Her automatic counter hits for 1.5 to 3.0 times her regular attack damage. She also boosts damage, with a solid 60% to three party members and 20% to the remaining two for a 44% boost average. Her 1.2x skill activation is always welcome. Can always have a good cry with Nerine.

Herb Peony (Hallow) / Snow Drop - Slow to build but massive 75% damage boost to your party. Peony gets an additional 5% and a 20% critical activation, Snow Drop gets 1.2 skill activation.

Mimosa - A more tanky, less evade-y Lycoris with a 60% solar drive damage boost. BUBBLES!

- - - ? ? ? - - -

Dogwood - (disambiguation required) With solid base stats, she can rack up a ferocious 75% bonus to party member damage but it's unclear if that bonus can be built up and retained over the duration of a subjugation or if it only lasts one battle. Her skill is also a mystery, listed as 3x damage to two enemies in the wikia and a mere 2.2x in nutaku's FKG. Her 1.2x skill activation is always welcome. "Starts the subjugation with 100% Light Gauge." is nice, but kind of weak to take up a skill and is worthless in redundancy and does nothing for raid fights.

Easter Cactus - Want. Can't has.

. . . Did I miss any good ones?

Take a look at Dendrobium