3eVolt should be considered the best regiment of the decade, it's the only regiment that's had a consistent competitive impact in pretty much every era of competitive NW, I would say its peak skill doesn't quite match the LG's S9 roster, because no one does, but if we're really talking about a decade and not month-long or 1-2 year spans, it should be 3eVolt, which was competitive since 2013 (although has disbanded/reformed a few times).
If 63e had continued to be relevant past mid-2016 I would potentially consider them, but I think 3eVolt continuing past that gives it the edge, but otherwise, kind of the same list fartknocker has.