All of them lol. Summers pushed aggressively for the free trade agreements (including allowing China into the WTO) that, in practice, shuttered American manufacturing, he pushed for cuts to capital gains tax, he lobbied aggressively against regulating derivatives and in favor of repealing glass-stegall, both of which directly led to the 2008 crisis, and then after the crisis he caused, he architected a recovery package that prioritized bailing out banks (but not enough to dig the economy out of recession quickly). He's one of the most damaging American figures of all time, he basically got us Trump if you ask me.

In general he was not a fan of regulating banks, although he walked back some of his beliefs after 2008. Although iirc he still supports combining investment and commercial banks. Various shenanigans involving privatization of Russian industry. Pushing for tax cuts at the expense of infrastructure spending. He didn't like that the US capped exec pay at banks that received bailouts (banks that gave him millions in speaking fees, which seems a lil bit sketch)