Landslides in Korea are one of the most common natural disasters because it doesn't need anything to trigger it except for gravity which is pretty common all around the planet. A landslide is when a big mass of rocks, debris, or earth is pulled down a slope by gravity. These are also called Mass wasting events, not to confused with wasting as in trash. These mass wasting events also include mudslides, rockslides, etc. in addition to landslides. 

The most recent landslide in Korea seems to have happened on July 7th 2021. Heavy rain in  the city of Gwangyang caused a landslide that destroyed several houses and killed one person. The deadliest landslide so far happened in 2011 on Jul 27th. Heavy rain in Seoul, South Korea's capital, alongside a northern town triggered a landslide killing 32 people and causing one child to go missing. About 800 houses were flooded and 23 roads had to be closed. To help prevent landslides Korea has taken to planting trees, controlling erosion, and doing inspections to vulnerable areas. They also have enforced piling sandbags and established retaining walls to help prevent landslides in urban and areas with a high population. 

Refrences: 

https://www.theguardian.com/world/2011/jul/27/south-korea-landslides-kill-17

https://floodlist.com/asia/south-korea-floods-landslides-july-2021

https://www.adrc.asia/management/KOR/Natural_Disaster_Countermeasures_in_Korea.html