Full Repertoire - Use all units abilities at least once.
Easy as pie, start up 2 skirmish games, one as Echelon the other as Sai. Use Scorched Arches map as you can use all unit types.
Spawn 1 of every unit (which will net Calling all Units aswell) & as soon as theyre ready, just choose each ability. Doesnt have to be used on the enemy, just has to be selected. Also the commanders equipment related abilities dont affect this achievement.
Once youve used all the plays, exit the game & repeat with the other faction. Should take 20 mins at most.
edit- The Spectres mind control ability must be used on an enemy. Thank you for pointing this out to me in the comments :)
I did this during the campaign as it more or less makes you. So apologies to those who didn't get what why the cheevo didn't pop.