which is the Hardest varient you think

for me atomic

For if you want the best strategy variant then it is Antichess most and then 2nd place - Atomic 3rd - Chess960. Other all variants do not have any strategy

racing kings is easy
hardest is horde

horde is hardest

Atomic is hardest

i think atomic is the easiest antichess has the most strategy but crazyhouse is the hardest

Crazyhouse.

The Horsey variant

Horde is very hardest variant

960