To counter HK and Gorosei regen you probably just need to sever their connection to the abyss
I don’t think haki is going to be it btw
No one takes me seriously when I bring this up, but, hear me out:
What if you just need to draw over the Mark? Or erase it?
Ms. Goldenweek was introduced in Little Garden, the first Giant arc. She's more or less using Runes here; using symbols to create magic.
IMO this is also foreshadowed by Nami's Arlong Tattoo becoming a Mikan Tattoo; you need to alter the Mark to change its effects.
In Little Garden, Goldenweek/Marianne's Color Trap only stopped working once the mark was BURNED by... Usopp's Fire Star, the same attack he used on Gunko.
When Saturn died, he was lit on fire.
Is fire the key to disrupting the Mark? But stronger fire?
Mother Flame... or... the Daddy Flame???
Sanji... kick that tattoo off of Gunko?
Germa was part of the WG and attended the Reverie. Any chance Gunko and Sanji... know each other?
If Gunko is Victoria, Kidd's Childhood Friend, her getting her arm cut off also tracks for obvious reasons. Killer cut off Hawkins' arm to save Kidd. Kidd cuts off Gunko's arm to free her from the Mark? (this ties back to Shanks losing his arm to Lord of the Coast)
Maybe you have to attack the Tattoo directly... with Conqueror's Haki?
"Cut nothing". Gunko is a foil for Bonney on some levels; a girl raised by the WG, what Bonney would have been, if she hadn't had her disease.
Zoro cuts Gunko's Tattoo, without cutting her? Like Monet in Punk Hazard, when he disrupted her Logia powers with CoC?
Zoro has flame attacks...
Zoro saving a woman Sanji couldn't by attacking the woman is... something. I'm 100% convinced Gunko will become an ally sooner rather than later.