First off, as the description states, you will need to do this achievement in a ranked match. It is also recommended that you find a boosting partner otherwise this achievement will definitely prove more difficult.
The first thing you want to do if you haven't already is to scroll to "Options" and then "Controls" from the main menu. You can customize whichever buttons you like for diving and kicking. Personally, I chose
for dive and
for kick but choose whatever you are comfortable with.
Now go to "Online" and then choose "Ranked". You and your partner should be in a party to communicate and search at the same time. The game will not tell you which opponent you are fighting against until the match begins so tell each other when you have found an opponent - hopefully you both match up. If not, back out and search again.
In order to get "total domination" you need to headshot your opponent all 5 rounds in a row. The person going for the achievement should choose the character "The Baz" (it seemed like his kick aims directly at your opponents' head. The opposing player should be "Redacted" (it seemed like the headshot hitbox on Redacted had more leeway than other characters but not 100% sure, though use him anyway). Choose whichever gem and outfit you like when prompted. When round 1 starts, the player who is "Redacted" does not do anything. The player who is "The Baz" should dive (using whatever button you customized for dive) and when your head is off the screen, press and HOLD the kick button (using the button you customized for kick). If done correctly, your character will kick "Redacted" in the head and you will see/hear "Headshot". Simply do this 4 more times and it will show that you have won by "Total Domination" and the achievement will then unlock. If you miss one or more headshots you will NOT get the achievement and will have to start a brand new ranked match to try again. Good luck.
Special thanks to my friend and boosting partner Flava1975 for finding "The Baz" strategy and testing out the method with me.