An easy way to win at the final age...
You want to have 4 Ion Turrets up (trust me, it's worth it) and simply wait to amass about 300k.
Your turrets will defend your base easily. When you get 300k, make a Supersoldier followed by 2 Shooters and then another Supersoldier followed again by 2 shooters. When you see your Supershooter emerge, use the orbital strike to finish off any lackeys and clear most of his path to the enemy base!
Cheers.
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