LAN server is by far the easiest to climb on due to the players using 4th world connections and pings arguably in the 4 digit values. Its how that faggot NEACE was able to milk his "Challenger" title for so long because his bitch wife was from there so he had excellent equipment and breezed through shit just perma pushing as Top Trynd.
Next easiest is probably EUW due to how the demographics there work and low team coordination.
NA is difficult because of ping and landmass size. You could have someone with 30ms in Florida playing with someone with 200ms in fucking North Dakota or some shit.

When I was playing on the JP server it was fucking awful. I had 4 accounts permabanned (and I do mean this) for no reason other than I was typing in English and those racist fucks were reporting me and getting me banned. This was circa 2015ish when the number of reports, no matter the case, could lead to a permaban. I didn't realize this until I finally got so pissed off after my 4th ban that it was due to "negative chat" and I finally put it together that I was typing things like
"don't push"
"drag soon, play safe"
and this was identifying myself as non-jap so they were reporting me.

Also, the queue times were fucking awful.