From the press release:

Because two weren’t enough.

MILLAR & MCNIVEN’S NEMESIS #1 THIRD PRINTING VARIANT (MAY108023)
Written by MARK MILLAR
Pencils and Cover by STEVE McNIVEN
Mature… $2.99
FOC - 6/24/10, On Sale - 7/01/10

MILLAR & MCNIVEN’S NEMESIS #2 SECOND PRINTING VARIANT (MAY108021)
Written by MARK MILLAR
Pencils and Cover by STEVE McNIVEN
Mature… $2.99
FOC - 6/24/10, On Sale - 7/01/10

Related posts:

1. Marvel Unveils Variant Cover to Millar & McNiven’s Nemesis #1
2. Nemesis #1 Sells Out and Returns With A Second Printing!
3. Mark Millar Auctions off the Role of the Villain in Nemesis!
4. Mark Millar and Dynamic Forces Announce Nemesis Charity Auction
5. S.H.I.E.L.D. #1 Goes Back To Press For A Third Time!