about sentai male human looking villains
As you've probably noticed, starting with Ohranger, male looking villains were much rarer in sentai than before (if evil rangers aren't taken into account, from Ohranger through Go-onger, there has been only three regular male human looking villains : Dr Hinelar (Megaranger); Gaja (Boukenger ) and Long (Gekiranger).
However, I've noticed something; counting evil rangers, most of the male looking villains appearing in sentai have been what I would call, for lack of better word, trolls; in other words, villains which main aim was messing with heroes and villains alike for their own benefit, which was more often than not, having fun; it seems that Toei is fond of those characters a shuman looking male villains.
In Aba, there was Abarekiller, who was having fun tormenting with the heroes (and the evolien) for his own amusement, not caring about anything else; Gekiranger had Long, (okay, he was the Big Bad, but when he appears, he's pretty alone) who has a lot of fun completely ruining the lives of everyone in the show (hero and villain alike); in Gokai, there is Basco, who plagues both the Gokaiger, many former heroes and the Zangyac, and having a blast doing it; and in Gobusters, there is Enter, (okay, he's almost the sole regular foe) who's having a blast in messing with the heroes.
Besides, Brajira (despite not being human looking, he's a Gosei (former Gosei) Angel, like the heroes) is a troll as well; and Juuzo, despite having a different characterization, plays somewhat that role in Shinkenger.