By Kieran King Manchester United fans have been left seething after Jadon Sancho kissed the Borussia Dortmund badge upon sealing his return on loan until the end of the season. Sancho spent four years at Signal Iduna Park, scoring 50 goals and providing 64 assists in 137 games, before moving to United for £73million in July 2021. However, the England international has failed replicate that form at Old Trafford, finding the net just 12 times and providing six assists in 82 matches. The 23-year-old has not played a competitive game since August either, following a public fallout with manager Eri…