It didn't seem possible ... but NFL defensive lineman Adam Gotsis has found a way to be even more of a badass -- by getting a sick, 3-foot tattoo all over his back and butt!
TMZ Sports has learned the 6-foot-4, Jacksonville Jaguars pass rusher hit up artist JB Tattoos to get an extra-large tat done of a Japanese Hannya mask -- which symbolizes wisdom and good luck.
JB -- who's located in Denver -- tells us Gotsis flew him out to Florida to get the ink done .