I'm sure the question has come up time and time again among horror fans, especially fans of slasher movies, which killer has the highest body count. Now obviously it depends on the number of movies that the killer has appeared in. The more movies, the more chance to slaughter. But even taking that into account, the winner by a long way it would seem is Jason Voorhees of the Friday the 13th franchise. Now there are a number of claims on the kills Jason has made, ranging from an over-the-top 300+ to a more conservative 146. And without personally actually watching all 12 movies. Although obviously you would discount the first and last movies, as in the first it's Jason's mother that does the killing, and the last movie is a reboot, so isn't part of the original series. Some people count the last movie in Jason's kill list, but I feel it would be wrong to do so. So, that said, based on research I've managed to do, this is Jason's kill tally.
Friday the 13th (1980) - As stated, none as we all know, his mother did it!
Friday the 13th: Part 2 (1981) - 10 kills (including Paul at the end).
Friday the 13th: Part III (1982) - 12 kills
Friday the 13th: Final Chapter (1984) - 13 kills
Friday the 13th: A New Beginning (1985) - 2 dream sequence kills, the rest are by Roy.
Friday the 13th Part VI: Jason Lives (1986) - 18 kills
Friday the 13th Part VII: The New Blood (1988) - 15 kills
Friday the 13th Part VIII: Jason Takes Manhattan (1989) - 19 kills
Jason Goes to Hell: The Final Friday (1993) - 21 kills (possibly 26, but 5 are unconfirmed as Jason kills).
Jason X (2001) - 23 kills (confirmed kills, there are more, but difficult to know how many).
Freddy vs. Jason (2003) - 19 kills
Therefore over 10 movies (again discounting the first movie), Jason killed a total of 152. A kill rate of over 15 per movie, which is much higher than any other slasher.