This has a lot of potential.
Loser Rangers starts out with a pretty interesting plot in that this one insignificant monster of the week is done with the life he is living. He doesn't want to be just a monster living a sham of a life! Pretending to be beat up every week for a power ranger's show off as if they're actually still doing something for their people. No, he tries to escape this life and be as one with the outside people. But not in a living normally kind of way, because one slip up and he'd be dead. So after hatching up a plan and teaming up with a rogue ranger... it's time to get to work in ensuring his livelihood as a free person (or monster).
I quite enjoy the underdog nature that Fighter D is and how he struggles to get in a good place both for himself and the other fighters one day. He has many flaws, namely his pride as a monster as well as being super squishy. So much as a proper poke and his cover is blown, making fighting interesting and scary for this weak wonder. The stakes are high against him! And it's enjoyable to see just how he'll overcome these obstacles now and in the future.
The artstyle is lovely and clean. Animation is passable and has its moments. The OP and ED songs are bangers! This anime has such a good thing going for it and I well look forward to what is in store in the future, because some of these characters go wild. The dragon keepers are a definite enemy, but some of these rangers might just be willing to side with our little fighter.