Valiance said:
I'd say GDI in the original command and conquer. Like, no joke, nod had NOTHING to counter some of their items. (and don't say a "quick and sneaky" attack bike is going to counter a mammoth tank, because you're wrong.)
Attack bikes are going to counter your mammoth tank ten minutes before it gets built, by coming and blowing your harvester up early game, starving you of resources, and running away if it looks like a serious counter force is coming to stop them.
Bikes build early in the tech chain, and one on one can break any GDI unit short of the mammoth (you can dance a medium tank to death, costing the GDI $850 for your $500 unit).
NOD bikes, when used against harvesters, are the one thing in the game that has no real counter
Engineer rushes don't have a serious counter either. Sure, there are infantry units that could toast the engy, but he's coming in an APC that'll just run your flamer/grenadier over, and well positioned/microed engineers
will get into a construction yard before a single GDI guard tower can kill it, or if the CY is too hot, steal a refinery, costing the opponent $2000 for a $1200 investment (assuming the APC dies).
Early in the game that can be fatal, because you can't hold back enough resources to build a second refinery that early or you get steamrollered by a fully active economy.
We had to reduce the starting unit size so that neither side started with an APC to minimise the engineer rush, but even then it was the decisive tactic on every map except Tiberium Gardens, because losing you contstruction yard halfway up the tech tree is a blow from which you will not recover. (On Tiberium Gardens there's a 2 square chokepoint into the bases that you can't get an APC into if it's got non-infantry units parked there).