To unlock the rare Honorary Bouncers Badge, you must earn the achievement ‘The Death Sentence on Twelve Systems’ which involves killing several Nova Blade, Dar’Manda and Dire Skull NPCs located within the phase door inside the Mek-Sha cantina.
To start the achievement, you must pick up the quest ‘We’re Wanted Men’, from your factions Quest computer on Mek-Sha near the arrivals terminal then speak to the droid HY-P3 in the cantina.

When speaking to the Bartender in the Slugfall Cantina, make sure to pick Option 2. After the cutscene plays you will wind up inside the phase room with a randomly generated hostile enemy (Nova Blade, Dar’Manda or Dire Skulls), the enemies spawn in a large group with more running in frequently so you may die once or twice. I suggest using Heroic Moment especially the Orbital Strike, Grenade & Flame Thrower if you have them unlocked.
If you don’t get the right type of enemies to help complete the achievement, you can walk past them and outside the phase and reset the mission in your Mission Log (L) to attempt to generate a new set the next time you enter.

Once the achievement is complete you will be rewarded with a Bound: Honorary Bouncer’s Badge to your characters Mailbox. You cannot claim extra copies for your ALTs from the achievement window, however the NPC vendor behind the bar in the Mek-Sha cantina will now sell it to you.

Finally obtained the Honorary Bouncer’s Badge from swtor