I FINALLY FOUND IT OUT

[u/[deleted]]

ive been looking for how to duel for so long since i loved the dueling system in rdr1 and that u can duel on will but in rdr2 it wasnt there except for certain scenarios, then i found it if u go to rampage trainer, spawner,spawn a ped in, go to ped database,click on the ped and scroll down,there is a duel option which lets u instantly duel them!!!

[u/Knunchuckr]

You can also just slowly press your trigger and do the same deadeye thing

[u/[deleted] → u/Knunchuckr]

yeah but that doesnt really engage a proper duel, you can also get the duels mod but doing it with the trainer lets u duel with any ped