That's not a dark pattern though. Potentially poor behavior, sure, but dark pattern, no.

"Complete your antivirus" has a pre-checked tickbox for a totally irrelevant product. And in the process agreeing to a license. That's pretty dark.

Maybe as someone with above-average technical ability this looks obvious to you. To a lot of people, it isn't. And this pattern is aimed at fooling the less technically literate.

Agreeing to a license in the EU requires an affirmative action (i.e. pre-ticked checkboxes are automatically a fail to comply)

The requirements to have unticked checkboxes predates GDPR.

yes it is, dark patterns refer to user-design decissions that arguably exploit human-weaknesses. In this case human-attention span (not noticing that you have to disable this option), lazyness(it costs effor to opt-out) and human confidence in authority (I trust avast with my AV, so I trust avast not to exploit my trust (but they do)).

It's example number two on the wikipedia page for dark patterns, Misdirection.