I can sum up why I don't like Soji Tendo in two words: God Complex. to elaborate, I didn't like how not only did he have one, but the series continuously fueled it. for starters, if you analyze his catchphrase, he's basically saying "I will become God". next, not only is he perfect at whatever he does, but from what I've seen, he won most of his battles with very little effort, and I don't think battles are very interesting if the hero barely ever struggles to win. it also didn't help that he was extremely arrogant about it and that he was like that since the first episode. then came the problems with Hyper Form. first the series added to his complex by practically saying " Tendo is so perfect that the only way for him to get stronger is for him to go back in time and give himself a power-up", but then he got the Perfect Zecter that let him use the other riders' Zecters and even take them while those riders were transformed, leaving them defenseless in the middle of battle
the only instance I could find of being able to stand Tendo was in God Speed Love, where aside from the opening scene (where he comes in out of nowhere, interrupts a battle, transforms, and beats everyone on both sides with ease), he turns out to be a more believable and even sympathetic character, which unfortunately was ruined by the ending where he essentially creates his own God Complex
if he had started out really arrogant and seemingly perfect, only to eventually get knocked down a few pegs and learn humility and how imperfections are what makes people human, then he could've been a good character, but that wasn't the case. so in the end, the problem with him was that he was a product of a bad idea for a protagonist that the writing staff only made worse