Saitama is naked in one episode, but nothing bad is shown at all.

Hammerhead is seen naked. Nothing bad is shown, only his back and buttocks.

Even though there are some sexual jokes, genitalia or breasts are never seen.

In Season 2, there is a female character is in a lightly revealing BDSM outfit.

There's a very curvaceous female character who wears a very tight dress that (although covering her) leaves her shapes very visible. This is especially the case in a few close-up shots, though these aren't specifically focused on her body.

Some monsters are naked. However, the way they are drawn covers up the genitals.

Suggestive outfits are worn. However, no nudity.

During a fight, a man is hit in his soft spot. This is for comedic effect.

In Season 2, there is a monster named Ms. Don-S. She wears a lingerie type outfit which is very sensual.

A man's special ability causes his clothes to rip off, but no genitalia is shown. This character is also very attracted to fighting, much like Hisoka from Hunter x Hunter.

There was a part where Garou went on a mass killing spree and that he chopped off a hand from a A class hero a lot of bliss was shown

Tornado verbally abuses whoever she talks to, and almost killed Genos at one point. She only stops when Bang scolds her for her actions.

Tornado has a very physically and verbally abusive personality.

The second season has more blood/gore

In the season 1 intro there is a part where you see organs

The show is about a ridiculously overpowered superhero named Saitama, who can defeat any living being, no matter how strong or powerful, in a single punch; despite this, the majority of the show is lighthearted and the violence is largely over-the-top, usually when the villains die. In fact, the violence is not intended to be disturbing, compared to other shows which have less strong visual violence and more psychologically disturbing scenes, and it's all mostly played for laughs.

The show has a lot of guts and gore but very little visual blood (so far). Monsters are sometimes killed in an explosion of guts however humans are rarely seen killed. The show is very careful to show little to no gore regarding human characters. The show is easy to watch for adults and is rarely if ever, difficult to stomach.

A monster destroys several entire city blocks with his fists, presumably killing hundreds of people.

A monster has its eye-stock ripped out, which leads to its intestines and entrails flooding out of the eye socket. Yellow blood is seen pouring out.

A monster accidentally crushes a man with his palm. Blood and tattered clothing can be seen on his hand. One of the few disturbing scenes, The death is portrayed to be funny.

A monster is punched into a building, killing her instantly. Blood is shown splattered across the entire building.

A monster is punched once, killing it. Its intestines and guts fly through the air and a character later picks up the monster's eyeball in a nonchalant fashion.

A man is shown training his body using extreme methods, to the point that he is described as vomiting blood and having his bones crack.

A cyborg man is slashed, punched and has his limbs sliced off in battle throughout the series. No blood is shown, just robotic parts and electricity. He is rebuilt by the end of the episodes.

Two monsters are accidentally sliced into pieces by their comrade. No blood is shown, but you can see the insides of their bodies and the intestines as well.

A monster kills a clone, not seen but blood is shown on the floor after.

A monster is punched and killed in a single hit. Neon-green blood is seen flying out along with green entrails.

A giant monster is shown only the bottom half standing, the rest of his body gone, not shown how but explained later.

A monster is hit in the chest and has a large hole in their body with there eye popping out of the socket from impact.

Ass is said around 4 times in season 1.

In season 1, a couple uses of mild language which have been mentioned already, but in season 2, there are quite a few uses of "Sh**" and "B****."

Frequently uses of "ass," "crap," and "bastard".

Not a lot of cussing.

A few uses of "damn" and "hell", there's never any strong language.

Some uses of words like "jackass" though very rarely.

Some characters are seen smoking

There's a character who smokes frequently, but that supports his characterization since he's a zombie, so he can't die.

Characters drink sake (a type of Japanese wine) in a few scenes.

A scientist is shown injecting his brother with a serum that makes him stronger.

In Season 1, Saitama punches a monster into a monster's eye. Monster's eye bursts and blood starts bleeding out of his eye.

The entire series is about heroes that battle against monsters and other villains that attack the Earth. As such, there are several battle sequences throughout the series that can be pretty intense.

Many of the monsters and villains in the series have creepy or frightening designs. This is balanced though with goofier-looking monsters that are clearly made to be funny.

A thief is attacked by a swarm consisting of thousands of mosquitoes. They cover his entire body and drain him of his blood within mere seconds as he screams. His eyeball can be seen shriveling up as this happens. The mosquitoes fly away, revealing the man's mummified corpse. This scene is very disturbing.

The "House of Evolution" looks very creepy, as it's filled with test subjects and other mutations. Biological experiments are shown floating in large tanks.

The overall violence in this series is shown in an exaggerated manner and avoids being realistic, and the worst of this always happens to monsters. So it avoids being put in the category of anime such as Hellsing or Elfen Lied. This is mostly because the series is a satirical action comedy anime, and it's meant to make fun of overused tropes in various superhero movies and shonen anime.