Isekai stories almost always have impossibly strong protagonists who are strong for no real reason other than to be a power fantasy for viewers/readers. Will, the protagonist of this show, is strong, but not invincible, and the audience can see the progress he makes in his training as he grows up. The arc where Will is raised by his undead adopted family is one of the most genuine and heartwarming things I've seen in a show like this.
Many detractors compare this show negatively to Mushoku Tensei because the shows have the same basic concept (a person being reborn and having a second chance to grow up in a fantasy world), but that's a pretty broad type of story. The key is in the execution. The most refreshing part of this show is that Will is actually a believable character. Many other stories try to pretend their protagonists have depth by giving them flaws like being cowards or perverts. Will's flaws are much more thought-out and suited to the story; those being that he can sometimes be reckless and put too much or not enough faith in those around him.
The biggest flaw of this show is that it didn't really need to be an isekai in the first place. With some minor reworking, it could have been a normal fantasy story. Regardless, Saihate no Paladin is some of the best the isekai genre has to offer.
