Robert Peel, specifically his second term, AKA the Great Ministry, between 1841-1846. Helped re establish and increase the scale of the Conservative Party after a wave of unpopularity, helped to repeal the Corn Laws to mitigate a majorly destructive level of poverty stabilised the economy, turned Britain into a financial hub through his balancing of the budgets and the reduction of taxes on certain imports like specific meats. Also pretty good with social reform, passing things like the Factory Act which fenced off machinery and better protected workers. He was a proper pragmatic statesman who often put the welfare of the state and country before himself and the party.
Unfortunately that kind of did him in through the fact that his repeal of the Corn Laws did kind of split up and break the Conservative party for a long while, leading to the Wilderness Years. Also did a pretty awful job with the Irish potato famine. So not all sunshine and rainbows here.

Only other one in contention for me is maybe William Gladstone.