Glad you think so ^_^

Honestly, kind of? Swapfell is a combination of Underswap and Underfell, swap is an AU where everyone's personalities are switched, sans and papyrus, alphys and undyne, toriel and asgore, flowey and temmie, etc etc. and fell is an AU where everyone's 'edgy' and murdery (like how the fandom views chara) and only flowey is actually nice. So swapfell undyne is Undyne with Alphy's personality but also a psychopath who purposefully performs awful experiments on monsters. XD

Thanks friend!