Originally, the first username of Hermanubis. Thanks to a running meme/joke perpetrated by Landshark about how (in response to Hermanubis doing something) “Super55 would have done that better!”, Super55 has entered forum lore.
Super55 has become the AH version of Chuck Norris (in terms of having unlikely 'facts' about him and unlimited superpowers). He has also featured in a few Series episodes.
By definition, as Landshark has pointed out, Super55 is 55 times more super than Super1, who is still considerably more super than Hermanubis.
By coincidence, Super55 is also a brand of pesticide and a tractor, as GBW learned by googling it.