Story highlights "The Walking Dead's" fourth-season finale airs Sunday night

As Carol, Melissa McBride has been at the center of some brutal scenes this season

The actress promises a "crazy" finale

Season four of "The Walking Dead" has featured some of the most brutal scenes in the popular series' history. (Yes, that's a warning for those behind on the show. Spoilers ahead!)

There was the gut-wrenching death of Hershel in the midseason finale, but there was also the burning death of David and Karen early on. It was a mystery who killed them, but it soon came out that Carol (Melissa McBride) did it to stop them from spreading a deadly disease through the prison.

When Rick learned what happened, he banished Carol from the prison, but she reappeared in the second half of the season.

Young sisters Lizzie and Mika were left under Carol's care after their father died, but it became clear that Lizzie had a skewed sense of right and wrong, and she killed her younger sister to bring her back as a walker.

Then Carol decided yet again that another survivor was too dangerous to live and shot Lizzie in the back of the head.

The reaction to this episode was huge. With McBride at the center of some of this season's more memorable scenes, CNN spoke to her about Carol's evolution and the finale Sunday night.

CNN: What was your initial reaction when you learned what Carol was going to have to do this season?

McBride: It was surprising to me that Carol was going in this direction, absolutely. But it also made a great deal of sense to me that they would take her in this direction. First of all it's a very interesting arc for this character, considering that she's lost her daughter; she carries so much responsibility for that, and also (she's) trying to navigate this world.

CNN: Is this the most challenging acting role you've ever had?

McBride: By far. This has been by far the most difficult, and certainly the longest-running. The most challenging and rewarding, for all the same reasons.

CNN: There was a powerful response online to the deaths of Lizzie and Mika; did you follow that reaction at all?

McBride: Yeah, I was really happy about the responses that came from that episode. Shooting that episode was remarkable and such a great experience. It all just came together in such a wonderful way. People talk about how "it needs to be earned." I felt what was necessary in this episode was absolutely earned. The emotional and critical response has been wonderful. The fans have just been phenomenal in their appreciation for that episode. What ultimately happened in that episode was controversial, but I feel like it was handled with such a sensitive approach. The build-up to it was just handled so well.

CNN: Have you seen the memes that have cropped up about the scene? The line Have you seen the memes that have cropped up about the scene? The line "Look at the flowers" has taken on a life of its own.

McBride: People are pasting people's faces over Lizzie's in the flower bed! (Laughs)

That's another thing I love about the fanbase: They have a great sense of humor. ... I'm a spoofy kind of person. I appreciate the humor, and it's a great way to offset the devastation that people on the show (are) going through -- it's sometimes very refreshing to see that stuff.

CNN: There's a segment of fans who like the idea of Daryl and Carol together. They haven't had too many scenes together this season, but is that something you might be pulling for?

McBride: I know that Carol and Daryl have a tremendous bond. Personally, I am living vicariously through the fans, I guess. I enjoy their passion. For some people, watching the show, it's a fun element for them. They're very passionate about their 'ships!

CNN: How do you react to the show's massive popularity?

McBride: I'm constantly amazed by the amount of different types of people that are aware of the show. After the episode with the girls, a gentleman who is 73 years old -- he said, "I've never written a piece of fan mail ever, but I had to write how much I enjoyed that episode." It touched me so much.

When I think of how far-reaching this show is, and how big it is, it's like trying to fathom the beginning of time, and I have to stop.

CNN: What's your favorite thing coming out of the show?

McBride: It certainly has to be the relationships within the cast and crew, and getting to work with the people I do. It's so tremendously fulfilling, and personally getting to play this character has been a dream.

CNN: What can fans expect from the season finale?

McBride: There's nothing I can say that hasn't already been said! Like every finale, (whispers) it's gonna be crazy!