The most powerful wheelchair right now is to brush up on NPCs' favor, make friends, and then NPCs will help you fight. The publicly recognized strongest wheelchair is of course Lind Armand himself, who has always been so, and to this day no one has replaced him.
After having a set of equipment called "Graduation", Undead will lose interest in completing quests and then engage in other activities, like building and decorating houses, racing games, idling to synthesize Undead, exploring, and so on, until the current "Graduation Set" becomes significantly outdated, then they will continue grinding.
Until now, there hasn't appeared an Undead with a "complete collection" philately obsession, not because they don't want to, but because it is simply impossible, with the entirety of Newbie Village Continent plus the Magic Land, the overall area has already surpassed that of Earth, with different events happening every moment, too many limited "plots" occur and then completely disappear.