Before I switch to the currently airing season, lets rank the bonus cures. These are allied Cure only. No evil cures they will be in the villains ranking later this year. No goddess cures either, they don't really serve the same purpose.

Cure Echo really only had one movie where she was relevant and she was quickly left behind.
Cure Tender serves as the driving force for Cure Fortune and probably would've been a better choice for Cure Fortune.
International Precures is a neat idea, I wish they tried harder to give them more personality beyond the Hawaiian Cures.
Cure Infini is the first ever male Cure and well rounded on both the dark and light alignments and comes with some inspirational quotes.
Cure Flower I find amazing as she acts as the perfect old master of precures opening the doors to potential plot points in the canon.
Cure Mofurun is what happens when your teddy bear starts talking, the missing ingredient to argubly the best precure team
Cure Pekorin I hate, it really cheapens the show to shoe horn her in as a cure.
Kiryuu Sisters there isn't much to them, they look like evil cures but even without transformations they fight as well as the Splash Stars
Cure Tomorrow is basically Chibi Usa from Sailor Moon, only a toddler and more adorable and the least annoying toddler character in fiction.
Cure Oasis served her purpose as the legendary Precure but never caught on too much, her design is based on the fake leaks that plagued the lead up to Tropical Rouge Precure's release which is unintentionally hilarious.
Sakagami Ayumi - Cure Echo - 5.5/10
Hikawa Maria - Cure Tender - 6.0/10
International Cures - Cure World - 6.4/10
Wakamiya Henri - Cure Infini - 8.4/10
Hanasaki Kaoruko - Cure Flower - 9.5/10
Mofurun - Cure Mofurun - 9.2/10
Pekorin - Cure Pekorin - 2.3/10
Kiryuu Sisters - Cure Wind/Moon - 6.9/10
Hugtan - Cure Tomorrow - 9.0/10
Aunete - Cure Oasis - 6.9/10