Giant monster are not actually spectacular in terms of stats. They are simply like a normal monster, but have a ×10 multiplier on their HP count. Their Power and Speed stats are unchanged though.
Note that a lot of Bosses are also Brutal.
In terms of stat calculations, Giant monsters do not apply a level offset (see Monsters#Stats). EG. To get the stats of a level 500 Giant, apply the calculation with 500, not 499.