UFC star Sean O'Malley and 6ix9ine made their bromance permanent this week ... 'cause Suga let the controversial rapper tattoo his '69' logo on him!!
The duo had a helluva weekend together in Miami ... clubbing, playing softball and eating expensive ass meals out in South Beach.
But, while the good times may fade away, there's one part of their bro-down that won't -- the wild new ink O'Malley got ... with Tekashi taking the matters into his own hands and doing the job himself!