Well, the title is slightly sarcastic, because I looked at another review, and that reviewer...well, me insulting people would be wrong. If you're looking for a battle anime, for the love of god, look somewhere that makes sense. Would you look for battle in a high school romance? No? Don't look for it here, either.

Honestly, this Anime is a thought experiment, in my opinion. For that, I do love it for what it is.
The premise, as in the title, is that the main character can instantly kill anything.
If you've ever watched an anime with a fantasy story, surely you've seen a scene where the MC punches a wall, and all the villains are intimidated, and then there's no fight, right? Well, this main character could probably slay gods- but he can't, or won't, shatter a wall with a punch. In fact, his killing ability leaves no trace at all. There's an animation the anime added, but that's because it's impossible to understand the plot visually otherwise. Would you be intimidated if someone dropped dead with no sign? Probably not, you'd just be confused. What happened? Is it a trick?
This story is about a main character who can't intimidate anyone. In other words, he can either kill someone, or do nothing. Once you kill someone, you've effectively started a war with their faction, and caused all sorts of trouble. In other words, once provoked, he will always be forced to start a conflict with a faction.

Side note, there's several scenes that I thought were excellent from the light novel, that got completely cut because they couldn't find a way to animate it (Characters who have the ability to pause time, or have a system tell them information, were largely cut). In that sense, if you want to fully enjoy the series, I do recommend the light novel.

In this fantasy world, fighting against crazy abilities is common, and many people have crazy abilities. I don't want to spoil any specifics, but essentially, these factions that want to kill him go about testing if they can kill him in different ways. It's suicidal against an instant death ability, but by collecting information, they hope to gather enough to eventually kill him.
That is the plot of this series. It's the author, creating countless overpowered abilities, and having all of them face off against the main character, and seeing if anything could kill him. "What if you stay out of sight?" "What if you send someone else?" "What if you attack without intent to hurt him?"
That is the plot to this series. It's wrong to say "There's no suspense." Obviously the main character is going to win- how many anime have the main character lose? The real question is "Can he deal with something like this, or will he reveal some other card?"

The animation isn't great. It's kinda cheap, and they don't do much, honestly. As mentioned, many light novel scenes that would be too expensive to animate seem to have been cut. Honestly, this series could have been significantly better if it had better animators and more effort put into it. For that reason, it's a 7. Personally, I rated it an 8, because I already read the novel, and seeing stuff come to life is extra nice.

Also, the anime actually does a relatively terrible job of fully explaining the main character's existence, who he is, how he works, and the things he's done. Read the light novel. But, if you want to watch a simple lighthearted fantasy anime, this is great.
At least I didn't have to watch a reincarnated "30 year old man on the inside" pretend he doesn't feel love just because the author thinks it would create social controversy, and have him struggle to realize his emotions or have any sort of normal human conversation. There's nothing annoying about this series, and all the conflicts will be eventually dealt with, and everyone will get their just deserts in one way or another. Personally, that's what I want in a series.
If you only like dramas, battle anime, or weak to strong growth- look elsewhere. Otherwise, give this a shot.