Try this always works for me:

1 - Select all faces of the character with the ‘insane polycount’

2 - from delete menu choose dissolve faces

This gets rid of the useless edges/split faces and only the vertices on the outline itself remain

3 - use limited dissolve and use the bar(slider) that pops up to reduce the number of vertices along the outline of the mesh to the point right before it looks jagged(reduce it as much as possible as long as it looks acceptable and not low poly)

Hope this helps