It once seemed like the indomitable Viktor Korchnoi would play chess forever. After thrice battling Anatoly Karpov for the World Chess Championship (once in the 1974 Candidates Finals that turned into a de facto title bout after the reigning World Champion Bobby Fischer forfeited his title in 1975 and then in official championship matches in 1978 and 1981), Korchnoi continued to play high level chess for several more decades. Korchnoi reached the Candidates round in 1985, 1988 and 1991 before winning the World Senior Championship in 2006.
Korchnoi retained a child-like enthusiasm for chess throughout his life. He played with great energy and tenacity.
He is on the short list of candidates for the title of "Greatest Player to Never Win the World Chess Championship," a subject that I explored in a 2009 article titled Uncrowned Champion: Viktor Korchnoi.
Korchnoi battled against six generations of chess players, as early in his career he faced opponents born in the late 19th century while more recently he battled against players born post-2000. He survived both World War II and the efforts of the Soviet establishment to crush his individuality and break his spirit by holding his wife and son hostage after he defected.
I have yet to see any public comment by Karpov about Korchnoi's passing. Karpov and Korchnoi were bitter rivals but one would hope that Karpov would have enough class, dignity and respect to say something positive about Korchnoi's significant role in chess history.