Create a character you want. Now head to https://cod.uberguy.net/html/category.html?pcat=mission_maker_attacks or https://cod.uberguy.net/html/category.html?pcat=mission_maker_secondary and start picking extra powers to give the critter. Only powers from those categories are allowed, everything else you enter will be discarded. Then, open your critter in Notepad (or the text editor of your choosing) and paste the powers' internal name into the critter with "Power" in front of them, then save the file: Only 25 lines of powers can be added, and as per usual AI, half the time they won't use them
These critters will NOT give XP when defeated. So, adding one to an existing XP giving group will help alleviate that. Or simply giving an ally a rez to make them more useful is also a thing.
When editing the critter it should look something like this.
Save and off you go.