Mr. Krabs, the character from SpongeBob SquarePants, did not actually die in the official TV show. Rumors and stories of his death originated from a fictional class project and internet rumors, not from an actual episode. According to these rumors, he was found dead in the Krusty Krab with a throat cut caused by a metal spatula, and there was speculation about who killed him, including SpongeBob and Plankton as suspects. However, these are entirely fictional and not part of the show's canon. Mr. Krabs remains alive and active in recent episodes of SpongeBob SquarePants.
There was also a deleted episode titled "Kwarantined Crab," which some fans mistakenly connected to these death rumors, but Nickelodeon removed it for reasons related to COVID-19 and not because Mr. Krabs dies.
Some fan content and "lost episodes" lore portray Mr. Krabs dying by suicide or murder, but these are not official parts of the SpongeBob storyline.