LONDON (Reuters Breakingviews) - Christian Sewing has had a surprisingly good year, but 2021 will be harder. The chief executive of 17 billion euro Deutsche Bank will most likely have to abandon his medium-term profitability target. Reviving a merger with rival Commerzbank is the most logical Plan B. A pandemic-fuelled trading boom, relatively low loan losses and heavy cost cuts have helped Sewing in 2020. Deutsche’s shares are up 17% this year, while the Euro STOXX Banks Index is down 45%.