Villain has been felt short in last few years.
It seems Kobayashi written sentai in recent years (Shinkenger, Go-busters, and ToQger) are more interesting IMO.
Shadow Line was very interesting, since it had such a nice variety.
It's kind of interesting that odd year sentai (Gokaiger, Kyoryuger, and Ninninger) has the least threatening and intimidating villain organization.
Zangyack was really weak; Deboth was pretty forgettable (except Candelilla and Luckyuro); and Kibaoni Corps may be the all time least intimidating, least threatening, and least interesting villain organization I've ever seen.