This season? Ole. It's not even close.
Ole
12 matches
5 wins, 2 draws, 5 losses = average of 1.42 points per game.
18 scored, 21 conceded.
Rangnick
24 matches
10 wins, 7 draws, 7 losses = average of 1.54 points per game.
33 scored, 33 conceded.
All while this was the team that Ole has built and trained over the last three years. Rangnick had a terrible last two months of the season, but before that he'd helped get us back into a decent position. He's also had to deal with a far worse injury crisis than Ole had. I realised during this match that of the five attackers that at the start of the season we would have expected to play most of the games, for one reason or another none of them were available for this match (or most of the last month or so). Ronaldo, Rashford, Sancho, Greenwood, Martial. Add Cavani also barely being fit in the second half of the season, Pogba being out, Fred being injured for a while, Shaw missing almost the entire second half of the season, Maguire, Lindelof and especially Varane all picking up injuries and constantly being in and out of the team. He's had a shit squad of players with an obviously broken dressing room, then had huge portions of the players out on top of that.
Ole had a relatively clean bill of health, with a team of players that he largely built and trained over the last three years. Yet he still managed to do worse.