If I use Parasect's "Lethargy Spore" Ability after a Pokemon has been attacked by Dustox's "Nadir Powder", how many counters are placed on the poisoned Pokemon during Pokemon checkup?
Lethargy Spore resets any specific number of damage counters for Poison to 1, therefore overriding Nadir Powder's effect of 8 damage counters for Poison.
Source: Lost Origin FAQ; TPCi Rules Team (2022-09-08)

Relevant cards

Note: All applicable cards may not be listed below.
SWSH11_5
SWSH11_5
SWSH11_10
SWSH11_10