Suggested by Brian Dean, I compiled monsters that were in Super Sentai but not used for Power Rangers. I had compiled this list before back when in 2001 on my site when it was the Sentai Time Capsule but I had to remove it when we changed format. I do not know the real reason why any of these were used. Next I will be doing monsters that appeared on the show but only in background and got no closeup.
Dairanger / MMPR Season 2
Boss Kamikaze and Teacher TelephoneThe gravestone was used for the Halloween episode but the three of these guys were the 3 idiots from Dairanger. They fought the Dairenoh (thunder megazord) twice but never died.
Bird Cage VagabondHe had a vulture inside him and captured people and had a peg leg until he got his golden leg back. I guess he wasn't used because of time.
Zilong and JiaxuI used another picture of them but originally they were red and green. They are actually the armors of two human warriors. Probably not used because there wasn't enough footage of them in armor or too much fighting Dairanger.
Duke of TrumpsAppeared in the movie, his conglomerate form appeared in a picture book of MMPR, which always made me wondered why we never saw that monster. An insider told me Saban and Disney had to pay extra for the Movie footage so sometimes they didn't.
Kakuranger/MMPR season 3
Bakeneko
Dorotabou
Konakijijii
Sunakake BabaaObvious why this one was not used, by her breasts.
Kamaitachi
Karakasa -- parts of it did get used for another monster
Yuki-Onna
Zashiki-warashiThe Bratboy's first form.
Ohranger/Zeo
KerisField commander who rules Machine Beasts with whip and has a human disguise and appeared in 3 episodes, probably not used because her outfit sort of looks like an S&M whipper. parts of it did get used for another monster
Bara BrainHis footage mostly dealt with the Ohranger out of uniform, probably why not used. Also most of the footage was him as a ball.
Bara PoliceParts of him were used for Electrotramp for Power Rangers in Space/Ninja Turtle team-up episode "Shell Shocked."
Carranger / Turbo
VV Goriin
DD Donmo
HH Wasshoishoi
II Goki-Chan
Norishiron Extra/FinalFinal was not used, Extra (above) was from the teamup with Ohranger.
Goki-ChanGot the name Rockin' Roach.
SS SutatanzoAppeared in the Carranger vs. Ohranger teamup.
Megaranger / in Space
Neo Bat Nejire
Rose Nejire
Canary Nejilar
Porcupine Nejilar
Illusionary Nejilar
Helmedor (Mega vs. Car)
Crab Nejilar (Mega vs. Car)Gingaman / Lost Galaxy
Rigurou
Amehoshi
Gaaragaara -- most likely not used because of the Hindu infulence, but according to Grnrngr.com, the costume might have appeared in the background.
Bammers
BazoogaGregory (Ginga vs. Mega)
Daitanikusu II 
GirumanikusuGoGoV/Lightspeed Rescue
Jeeruda -- parts of it did get used for another monster
Deathmime
Buroogen
Hirugemuuja
Bahamuu
Big Douser
Garubaria
Golomois Giant Form
Beast Demon King GolomoisTimeranger/Time Force
Reihou
Vincent
Zektar
Banjan
Harbal
Boribar--parts of him was used for something else. His other form Pierre Bori was used for Quarganon. Gaoranger/Wild Force
Copy Org
Glasses Org
Human Body Speciman Org
Vase Org
Charcoal Grill Org
Blacksmith Org
Christmas Org
New Year's Org
Rakushaasa (Gao vs. SS teamup)
Zeus Org (Movie)
Hades Org
Poseidon Org
