Player A attacks and flips a heads for "Agility". Then Player B uses Single Strike Urshifu VMAX's "G-Max One Blow" attack; would this ignore Agility?
In this case, Agility would be considered an "effect on the Defending Pokémon" and therefore G-Max One Blow would be able to overcome Agility.
Source: PUI Rules Team (2005-02-17); TPCi Rules Team (2021-05-13)

Relevant cards

Note: All applicable cards may not be listed below.
COL1_45
HGSS3_28
EXP_12
EX5_9
SWSH5_86
SWSH5_86