Does Chara remember the reset and erase the world??
Without a doubt, Chara remembers the erasure of the world. The second time you complete the genocide route, Chara has a different dialogue.
Chara is also able to remember after resets. This is evident when Chara faces Sans in the genocide route. By reading Chara’s expression, Sans is able to tell how many times Chara has died to him because Chara is the one who remembers. Sans is also able to tell when Chara has killed him previously.
While this is generally seen in between reloads of the same run, this dialogue is also made between resets. For example, a player may defeat Sans in the genocide route, but reset before going to Asgore. If a genocide route is repeated on this new route, Sans will still comment on Chara’s expression: “that expression that you’re wearing… well, i won’t grace it with a description.” Having defeated Sans before, Chara was likely showing an expression of delight or triumph. This happens regardless of the number of resets since the last genocide route.
The pacifist route ending after the genocide route is also evident of Chara’s ability to remember between resets. No matter how many resets are done since the first genocide route, normal or true resets, Chara is in control at the end of the pacifist route.