Also known as: 踏みつけ, 踏み付け, 踏み潰し, 踩踏
When a character is in the process of forcefully Stepping on someone or something. Motion Lines can be found in these posts.
For when just a foot is on someone but there is no stomping motion, see Stepped On. If the foot is in the air before stomping tag with Imminent Stomp or Stomping Viewer.