They made Shane a bad guy before they killed him off. They made Andrea and Laurie annoying as hell before they killed them off. Dale had become a parody of himself before they killed him off.
Before they ever kill off Daryl and Rick, they'll make them unlikable characters or bad guys.
They would never pull a Ned Stark, Robb Stark or Oberyn Martell. But the writing and dialogue for the characters in TWD is so far below that of GoT that I can't imagine I'd care if they did.
Ned was arguably the main character of the whole first season, and still remains in the top 4 most popular characters of the series. He was killed off in S1 episode 9.
Robb Stark, though not as popular as Ned, gathered a big following and was assumed by most to be the one to avenge his father's death and defeat the enemies. He was unexpectedly and brutally murdered, without even being given the chance to defend himself.
Oberyn Martell almost instantly became a fan favorite and had his head smashed after only eight episodes.
No way would TWD ever do anything as risky.