On 2017-08-10, a new version of Vivaldi was released, with a new icon. https://github.com/KDE/breeze-icons/blob/master/icons-dark/apps/48/vivaldi.svg still shows the old icon. The new icon is visible and available on https://vivaldi.com/press/, and notably, a SVG version of the icon is available in the downloadable Press Kit. So, this icon needs to be updated.
Git commit ed7df288eda31fb52287082a129fec9c58f5af52 by andreas kainz. Committed on 28/12/2017 at 12:40. Pushed by andreask into branch 'master'. remove Vivaldi icon cause the origin app icon fits perfect with breeze D +0 -25 icons-dark/apps/48/vivaldi.svg D +0 -25 icons/apps/48/vivaldi.svg https://commits.kde.org/breeze-icons/ed7df288eda31fb52287082a129fec9c58f5af52