The 1994 Linares tournament with an average ELO rating of 2685 was the first Category-18 tournament ever held. Karpov played the best tournament chess of his life to win this tournament with a staggering 11 points out of 13 possible dominating the second placed Kasparov by a huge 2.5 points. His tournament performance at 2985 was the highest performance rating of any chess player in any tournament in all of chess history.
Karpov on Wiki, ChessGames, Biography & Brief Profile
Below i give a game from the 4th Round of the historic Linares 1994 tournaments which is probably one of the greatest games played by Karpov.
White: Anatoly Karpov
Black: Veselin Topalov
1. d4 Nf6 2. c4 c5 3. Nf3 cxd4 4. Nxd4 e6 5. g3 Nc6 6. Bg2 Bc5 7. Nb3 Be7 8. Nc3 O-O 9. O-O d6 10. Bf4 Nh5 11. e3 Nxf4 12. exf4 Bd7 13. Qd2 Qb8 14. Rfe1 g6 15. h4 a6 16. h5 b5 17. hxg6 hxg6 18. Nc5 dxc5 19. Qxd7 Rc8 20. Rxe6 Ra7 21. Rxg6 fxg6 22. Qe6 Kg7 23. Bxc6 Rd8 24. cxb5 Bf6 25. Ne4 Bd4 26. bxa6 Qb6 27. Rd1 Qxa6 28. Rxd4 Rxd4 29. Qf6 Kg8 30. Qxg6 Kf8 31. Qe8 Kg7 32. Qe5 Kg8 33. Nf6 Kf7 34. Be8 Kf8 35. Qxc5 Qd6 36. Qxa7 Qxf6 37. Bh5 Rd2 38. b3 Rb2 39. Kg2 1-0