You only seem half-serious, so I suspect there's something I've missed about KDE corner history.
Anyway, 'picom' can at least grind down those edges (or smooth out, depending on your point of view)
#################################
# Corners #
#################################
# Sets the radius of rounded window corners. When > 0, the compositor will
# round the corners of windows. Does not interact well with
# `transparent-clipping`.
corner-radius = 5
# Exclude conditions for rounded corners.
rounded-corners-exclude = [
"window_type = 'desktop'",
"window_type = 'dock'",
]
Anyway, 'picom' can at least grind down those edges (or smooth out, depending on your point of view)