Even though i haven't watched that many Super Sentai yet i would say Zyuranger it really felt like a chore to try and get through all of it

I would have to say Boukenger and Ninninger.
Both shows sounded awesome on paper at first and the art direction still to this day are some of my favorites, but both shows lost my interest quickly. I would try to keep on watching in hopes of it being better and there were a few eps along the way that were nice but overall did not cut it for me.

Definitely have to say Boukenger and Go-Onger. While there have been other shows I wasn't a huge fan of, they all had enjoyable aspects going on. These are really the only Sentai shows that had next to nothing going for me. I didn't enjoy Boukenger's characters at all and thought it was a waste of, honestly, one of the better cast we've seen in Sentai in the last two decades. While I loved Eiji and the climax to his story, it was nowhere near enough to save the series for me.

Go-Onger I dislike mostly because of the lackluster comedy. There was a time when anyone who didn't like Go-Onger was labeled as someone that didn't like fun, but I think that's an easy way to ignore valid arguments. Go-Onger, IMO, was comedy done really poorly and often just aggravating to watch. It's also another one of those shows that I thought so completely wasted a fantastic actor in the form of Hidenori Tokuyama, who would have been a perfect fit in a more balanced show.

I would say ninninger on top of my head because I hated the grandpa's personality and Red's monotone catchphrase/acting. I got used to Ban and Daigo, but he's horrible along with Lucky now. We haven't gotten strong menacing villains in a long time and there's way too many characters to cover in Kyuranger, so I hope it'll find the right balance.

But Kyuranger HAS Balance. :lolol
Jokes aside it is a shame Takaharu's actor did not meet up to expectations.

I'm not finished with it yet, but judging solely from what I've seen, I'm gonna have to go with Jetman.

Same, currently at 18. Though it's not necessarily bad, just my least favourite. Kyuranger hasn't gotten enough episodes for me to make a good judgement

It might be dated for you guys. I mean I was turn off by the quality until Gokaiger introduce me to check out the old series. Still wish Gokaiger done more with the useless Zangyack. Liveman and Dairanger are one of the top classic besides Jetman, so maybe you guys should check them out.

I'm enjoying Jetman but it's still rather weak imo. Dairanger's already on the backlog

It being old isn't my issue, I just can't bring myself to care about most of the characters. Out of the main five jetmen I only really like two, those two being Owl and Swallow, and they get pretty much no focus. The other three are either boring, like Eagle and Swan, or I absolutely loathe them, like Condor.
The villains also aren't near as great as most people make them out to be, so that was a bit of a let down.
Love the theme and suits though.

Dairanger, on the other hand, is flippin awesome. I haven't seen anything of Liveman.