Archie was actually killed by Rumplestiltskin (Mr. Gold) in the first season. He was accused of being a thief and was going to be executed by the townspeople. Rumplestiltskin offered to save him in exchange for his magic bean, which Archie had found. However, Rumplestiltskin secretly planned to use Archie's death to manipulate the situation and frame Snow White.
While Cora was a villain, her primary goal was to protect her daughter Regina, and she was often cruel and manipulative. Cora's primary role in the story involved her own ambition and trying to control Regina's destiny.
It's important to note that the show often plays with flashbacks and reveals information gradually, so it's possible to get confused about events. However, in this case, it was clearly stated that Rumplestiltskin was responsible for Archie's death.