Swimsanity!

Easier with a second player/controller, but here are the steps for doing it solo:

Start a game of versus, timed mode. Set the timer to 3 minutes (the lowest it allows).

For opponents, just add one bot (the game will fill all the slots, but you can press to remove unwanted bots). Be sure to set the difficulty level of the bot you will be facing to 'Easy'.

Once the match starts, you will basically just run away from the opponent. If you get killed, go ahead and kill the opponent so you are matched in kills.

When there is about 30 seconds left, get a kill that puts you in the lead.

After that, let enemy kill you so it is tied again. At this point, the timer should end with the two players tied.

When the timer ends and both players are matched in kills, Deathmatch starts. There is nothing special here I noticed (no one-hit kills or anything crazy). Just kill the opponent like normal and the achievement will unlock on the stats screen.