From this post:

Vivaldi's approach to privacy almost made me laugh, "we block others from tracking you so we can do it ourselves"

When you install Vivaldi browser (“Vivaldi”), each installation profile is assigned a unique user ID that is stored on your computer. Vivaldi will send a message directly to our servers located in Iceland every 24 hours containing this ID, version, cpu architecture, screen resolution and time since last message.

If being fingerprinted by hardware wasn't bad enough, your literally assigned a unique id, don't even bother defending vivaldi on this one.

Vivaldi is proprietary so no one can audit the browser, no one can fork it to remove spyware, you base everything on blind trust.

Their new tab is bloated by tracking companies meaning on each new tab a query will be made to amazon, youtube etc. Sure you can remove these, but most people won't and it shouldn't be included by default.

Its default search engine is bing, how great, so "we at vivaldi care so much about user privacy that we recieve monetary gain from microsoft by sneaking that little search engine in, which a huge percentage of our users will use as they're not aware of the privacy issues because they trust vivaldi"

We at vivaldi block trackers so we can boast about it, but our adblocker is disabled by default because we dont want anyone using it.

Google safe browsing is on by default with no proxied option

It uses googles blink engine, which is fairly common so i can't hate on it for this alone, but bare that in mind.

I used edge as an example, dont actually use edge for privacy.