There's a semi-common meme on Twitter where people share their most X opinion, where X is a group the poster doesn't identify with; or sometimes my least X opinion, where X is a group they do identify with. In that spirit, my least libertarian opinion is that exclusivity deals with sufficiently entrenched companies* are bad and should be illegal.
Elizabeth Warren recently proposed a wealth tax as part of her plan to partially pay for single-payer healthcare. I think this is significantly worse than other methods of raising the same amount of revenue from the same group of people, so this article describes the problems with wealth taxes plus an alternative if we want to raise tax rates on the rich (spoiler: just raise the income tax rate).