1. Titan – Giant (Attack on Titan)
One of the most haunting character images in manga/anime. Titans in Attack on Titan are cannibal giants. They have a large stature, formidable strength and extremely brutality, always threatening the danger of humans no matter how they hide.
2. Evolutionary Cockroaches (Terra Formars)
The story of cockroaches sent to Mars by humans 600 years ago. In the environment of Mars, the small cockroaches of the past 600 years have evolved and gradually resembled humans. Not only that, these creatures become even more terrifying when they have amazing health and superior evolutionary ability that allows them to confront and destroy most of the expeditions sent from Earth. .
3. Gauna (Sidonia no Kishi)
Gauna is a giant alien monster with the ability to change shape. They are so powerful that they can destroy the entire Earth. However, each Gauna has an almost impenetrable core protected by a large mass of matter known as the “placenta” – the placenta, commonly referred to as “Ena”. Once the placenta is blown away and the nucleus is destroyed, Gauna’s entire body will disintegrate.
4. Mutant Fish (Gyo: Tokyo Fish Attack)
The whole of Okinawa was stinking, and it wasn’t long before Kaori and friends realized that the stench was emanating from dead fish rising out of the sea. The fish have metal legs and are infected with a strange disease that can infect humans, created as a weapon with a mysterious source of energy. Almost after a short time, the whole of Japan was invaded by this animal.
5. Tatari Gami (Mononoke Hime)
Tatari Gami is not the name of another god, but all the gods in the forest can transform into Tatari Gami when its anger and pain exceed its limits. When that happens, a black fluid shaped like worms will sprout from its body until its whole body is covered with the fluid. Once completed, Tatari Gami can use those tentacles to move and attack. Anyone who is infiltrated by this fluid will suffer a slow and painful death.
Source link: List of the scariest monsters in Manga and Anime
– Emergenceingames.com