The save games are located in <Documents>\My Games\STEEP\<UserProfileID>\.
On PlayStation 4, save games are located on the PlayStation hard drive. They can be deleted by accessing the PlayStation Settings > System Storage Management > Application Saved Data > Saved Data in System Storage > Delete. Select Steep and delete the save files. There may be up to two save files per profile.
Save games are located on the Xbox hard drive, as well as on the Microsoft cloud. They can be deleted by accessing the Xbox Dashboard and going in Games > Steep > Options > Manage game. Select the Steep save file and delete it. There is only one save file per profile.
Deleting the save files will not affect the entire multiplayer progress. The multiplayer progress (such as leaderboard, items, money) is saved on Ubisoft servers and cannot be deleted by the player.