1. Virgil van Dijk
Reported fee: €84.65m
How could have there been a shadow of a doubt regarding the ultimate spot on this list? After the sort of year (and career) that Virgil van Dijk has had with Liverpool, there is hardly room for any doubt.
Liverpool's colossus in defence has been the gold standard for central defenders since his record-shattering move from Southampton back in the winter window of the 2017/18 season. Having moved for a fee of €84.65m (£75m) to Anfield, both the club and player were subjected to the brutality of keyboard warriors all over social media, mocking the big-money move.
This transfer has, however, single-handedly turned the fortunes of a perennially struggling defence, taking them from a mid-table backline to that of the champions of Europe.
The former Celtic man has it all: he's mighty strong, imperious on the ball, aggressive in the air, a clean tackler and most of all, an unbelievable reader of the game. Van Dijk's presence and presence gives Liverpool the sort of confidence their other outfield players need to venture up the pitch, often bailing the team out with his sublimely timed interventions at the most crucial moments.
The Dutchman has won innumerable accolades over the past year or so, having lost out to Barcelona's Lionel Messi in the running for the Ballon d'Or. He was named UEFA Player of the Year and Defender of the Season, PFA Player of the Year, and Premier League Player of the Year for his herculean performances over the 2018/19 season. Additionally, considering Liverpool's 10-point lead at the summit of the Premier League table, van Dijk is perhaps a soon-to-be Premier League winner as well.
Of all of Klopp's signings, he has arguably been the greatest and is on the path to becoming one of the most complete central defenders of this generation.
Virgil van Dijk could go down as one of Liverpool's greatest ever transfers in their illustrious history.