Board Thread:Questions and Answers/@comment-25259448-20140803091122/@comment-34326521-20140803095112

The method you suggest for Clockwork's "duplication" would make the weakness you mentioned non-existent, under Ben 10 time travel physics. When Gwen changed the past (which is what Clockwork would be doing, since his past self wouldn't do the same thing his present self did), she traveled to an alternate timeline. Therefore, although the Gwen from that timeline had been killed, the Gwen from the main timeline was alive. In short, even if Echo Echo destroyed one Clockwork, it wouldn't do anything to the others. In addition, Clockwork can slow down time around himself. With an army of Clockworks, this would make him impossible to beat. At least by Echo Echo.

Then there's Jetray, whose neuroshocks at 1/10th their average power were able to destroy Echo Echo clones in one hit (Ultimate Kevin, anyone?).

Way Big can also do it, unless Echo Echo can divide tens of thousands of times before Way Big has a chance to fire his Cosmic Ray.

Swampfire is virtually indestructible, since he can regenerate from any number of pieces. So are Goop and Upgrade, and all of these have fairly powerful offensive capabilities, with the weakest, IMO, being Goop, who can simply become acidic and spread across a large area.

I can probably come up with more, but I think this is enough.