Pick a Zeon pilot and choose the third or fourth stage. Wait till you get to a space battle and G-Bull will be there. Kill it with a mobile suit (ally can't make the kill)
Pick the fourth stage in arcade mode. On the
second stage, Big-Zam and another mobile suit. Kill
it with a Gundam with a Hyper Bazooka, Hyper
Hammer, or Beam Rifle (go for the legs, the Big Zam
is weak and can be affected with the Beam Rifle
if you hit its legs). You can use a Beam Saber and
other mobile suits to kill Big Zam. Once you do
that, it will be in vs. mode. (can't be killed by ally)
Extra Campaign Mode
Beat campaign mode with bothe the Federation and Zeon.
Pick a Federation pilot and choose any stage. Wait
till the Belfast Base level is shown. Grabro will
be there kill it by yourself with a mobile suit.
(ally can't kill it)
Pick a Zeon pilot and choose the 4th stage. Wait
till a forest stage and a Guntank and G-Fighter
will be there. Kill G-Fighter by yourself to
unlock it in vs. mode.
Choose the third or fourth stage and when it's
the second to last stage, Braw-Bro will be
there. Kill it with a mobile suit (ally can't kill
Pick the first stage in arcade mode and when you
get to a desert mission,Adzam will be there with
a Gouf. You must kill Adzam.