SCP-RL
Object Class: Keter
Special Containment Procedures: Because of its size, SCP-RL cannot currently be contained, researchers are working on containment. The location of SCP-RL is not precisely known, but imaging satellites and analyses of eccentricities in the Earth's orbit suggest SCP-RL is located in the Atlantic Ocean, and Arctic Ocean.
Description: SCP-RL is a massive creature. Fins and head protrusions included, the creature is just a little shorter than a submarine owned by the Foundation. SCP-RL possesses a long, slim, muscularly built body with four caudal fins and two pectoral fins. It also has two dorsal fins running along the length of its entire body, and two ventral fins taking a small portion of its belly. Most of its fins, along with its back, are red in color. Its head features a large mouth, as well as two pairs of eyes with grey sclera and dark green irises. It has two maroon mandibles on each side of its face which slowly get darker, tipped with black claws, four in total. Multiple scars can be seen on the body, particularly around the facial area, and the bluish-white skin appears similar in texture to human skin.
The Reaper Leviathan emits loud, echoing roars audible from great distances, this roar is a form of echolocation. It also seems to circle its prey for a few moments before attacking, and often strikes from behind by surprise. If the Reaper Leviathan manages to grab the targeted prey, the creature will hold its victim in its mandibles, pause for a second while roaring, and then proceed to pull the prey into its mouth, killing them instantly. When the SCP-RL is exposed to damage, it will flinch and roar shortly after being hurt.
SCP-RL has been observed to grab small submarines with its mandibles and smash it down to the seabed, destroying it completely afterwards. It can and will also destroy bigger submarines
Assessment: Extreme threat - Avoid in all circumstances
(I am aware this is from the game "Subnautica" i thought it would make a good SCP)