Gentleman is a villain and former team member of Cyborg Resistance.
Mako was one of the first people recruited to the Cyborg Resistance. He initially took up the position of Jewel Man, but after a dispute with Riker (at the time using the persona of Jesus Christ Man), became Splash Man. Seemed to do absolutely nothing on the team.
During his 'tenure', however, several bizarre accounts popped up, several of them being scat-related. At least one used Mako's IP address and at least one other (named Scorpio's Wisdom Teeth) was created for the sole purpose of pissing off Scorpio, the team's Galaxyman.
The tipping point came when Mako vandalized his own account to become 'Brony Berget' and, when confronted by Scorpio about it, blamed Sinistar and Psycho. After some discussion between the two and Scorpio, Mako was outed as a hardcore brony (something that did not endear him to Psycho OR Sinistar), confirmed as the source of all those bizarre accounts, and, of course, revealed to have vandalized his own account, as well as other non-team-related unpleasantness. He was kicked off the team and IP banned from the forums after that, and his spot was filled by Silver Dime.
As a team member
Gentleman was originally one of the eight members of the Mecha Badasses, but after their disbandment, he and Sinistar were the only members left. The two eventually entered the Cyborg Resistance; Sinistar became Magma Man, and while Gentleman was aiming to become Tornado Man, he got turned into Splash Man (basically Splash Woman with a beard, monocle, and top hat) instead by Roll, as revenge for some blatant sexism on Gentleman's part. Oh, and he got beaten up on by the rest of the team at the end of Fakeman's Origin.
In Splash's Cluckity-Cluck-Cluck Day, Part 1 consisted of him basically being used to get free stuff from people because of his "shiny new feminine wiles" to attempt to con people out of stuff... which leads to the death of three people. They board a plane out of the country, which the rest of the team ends up being on. The plane crashes, leaving the team stranded, and Gentleman is unceremoniously kicked off the team once Silver shows up.
As a villain
After being thrown into a chasm by the rest of the team, Gentleman is discovered by four mysterious figures, and is defused from the Splash armor. At the prompting of these strangers, he decides to take revenge against them. After an encounter with the Red Squadron, Gentleman is revealed... in a big-ass robot. After much effort by the Cyborg Resistance, Gentleman reveals the robot is only weak to laser attacks; cue Silver becoming the new Splash Man and kicking Gentleman's ass.
In the first part of Lights, Camera, Action Jacktion!, it's revealed that Gentleman had Action Jacktion and his family murdered in order to apply for the Mecha Badasses. Gentleman is revived by the Blue Squad, and fights Action Jacktion, himself revived and put into a Magma-Man-esque suit by Sinistar. Action Jacktion defeats Gentleman again, but dies shortly afterwards.