Serious Sam: Siberian Mayhem

Basic Info about achievement:
To be able to ride a Draconian Burner, you need to have the Rodeo Time skill learned which requires a minimum of 4 Skill Points to obtain. Once you have the skill, when standing behind the Draconian Burner, you will be prompted to press the melee button to mount it. When mounted, the attacks are primary fire button shoots the burners and the secondary fire button does a ground smack. Note that the Draconian Burner cannot take much damage from other enemies and there is a time limit of how long you can ride it.

Recommended location:
A good place to get this is during the side mission Alpha and Omega on Mission 4, Roadside Picnic. Before entering the tunnel I recommend making a save point so you can retry if necessary. A few groups a small enemies will spawn followed by the Draconian Burner as you travel through the tunnel. I initiated Time Warp gadget when the first group of enemies spawned, ran past them until I reached the Draconian Burner, mounted it and easily killed everyone. Use the secondary attack ground smack for the close enemies and the primary attack burners for the far enemies.
When I did this, I scouted the area first to see where the enemies spawned and then got it done after reloading the save. Lower the difficulty if need be while doing this.

Link to Draconian Burner info (for those who don't know what it looks like):
https://serioussam.fandom.com/wiki/Draconian_Burner