That means how he feels about Breaking Bad's Walter White just that much heavier.
The "A Song of Fire and Ice" author wrote on his blog after watching the Breaking Bad episode "Ozymandias" "Walter White is a bigger monster than anyone in Westeros." He sought to remedy that.
In the same blog, Martin wrote the episode influenced him to write an even worse character in future books in order to "fix" Breaking Bad's claim to the nastiest character. That's coming from a very dark place when the guy who wrote The Red Wedding says it.
It'll be tough to prepare for that one. Don't grow too fondly of any character.
