My headcanon so far ist you probably need a critical mass on haki to severe the connection between the opponent and the abyss
If the OPP has COC he can use defensive however the connection is harder to severe because even if you have better haki than your opp a certain amount of the attack gets diminished
So that's why only a big Kamehameha haki can truely go for the kill shot. This is also not something you would do in a real right so it's something you need to figure out. This also makes sense that despite gabs previosly fighting his but not knowing now
Exteeme headcanon however i probally used more braincells than oda on this one
@Kurozumi Wiwi @grey matter @Sentinel