 If you liked
Tensei shitara Slime Datta Ken
|
 ...then you might like
Ore dake Level Up na Ken
|
Both main characters start off weak and progressively becomes stronger, gaining new abilities and gear by battling monsters.
Both main characters hide their true strength.
Solo Leveling seems to be inspired by Tensei shitara, in the sense that both of the main characters interact with a system UI unique to them.
Both animes are set in a fantasy MMO RPG like world, with Solo Leveling being a crossover between the modern world and fantasy.
Tensei shitara focuses on character development and world development. Solo Leveling is mostly focused on character development, but both animes still have a similar vibe.