28. ... Ne4 ?
Better: 28. ... Nh5 ! (a knight on the rim is not always grim) threatening both 29. ... Nxg3 and 29. ... Nxf4 followed by 30. .... Bxe5 winning material. After that white can resign.
If you miss such basic tactics then you don't need to wonder about opponents which are "extremely difficult to beat".
In this game my opponent was extremely difficult to beat despite being ranked a lot lower than me. He created many threats and slowly started clawing back the material he'd sacrifced to get an initiative. Luckily, I was finally able to find a pretty mating pattern and pull through.