@ituhabitu For the past few months, there have been several threads in this Mac forum about crashes. From those threads, I've drawn these two conclusions:
Deleting your user profile will very often cure the problem.
Some of the crashes are likely due to a bug in macOS, which Vivaldi or Chromium developers haven't been able to address.
So, your options are 1) wait or 2) delete your user profile and see what happens.
If you keep having crashes and if you have a crash after upgrading Vivaldi to the latest version, be sure to submit a crash report and wait for the next upgrade.
Me, I had frequent crashes for some time. I just waited and kept submitting one crash report per upgrade. Then the crashes eventually subsided. I'm pleased that I've gotten through the period without having to delete my profiles.