Ork sizes

In life, in the stinking flesh, the orks were colossal. Every single one of them was as big as a Space Marine. They simply radiated weight and power, from the huge knotted masses of their shoulders to their treelike forearms and wrecking-ball fists. Laurentis had never seen creatures express such manifest strength and density by simply existing. They were muscle and power, they were fury and rage, they were raw noise and brute strength. They were truly monsters.
...
	The Beast was not the Archfiend of Urswine, however. The Archfiend’s invasion force, while a savage sea of green into which Imperial worlds went to die, were mere runts compared to the Beast’s hulking monsters. Amongst the Beast’s countless number, the Urswine orks would have been trampled under foot. Even the greatest of the Archfiend’s brutes – perhaps even the Archfiend itself – would have been lost in the shadow of the Beast’s invader savages. The puniest of the Beast’s monsters were small mountains of muscle, standing snaggle-jaw and shoulder over other orks. Striding through the mobs and madness were greater beasts still: towers of tusk, green flesh and ferocity. Like gargants or giant effigies of greenskin gods brought to life, these hulks carried colossal weapons that demolished buildings at a single strike and monstrous guns that mangled infantry and tank formations with equal, bloody ease.

I am Slaughter