Ravage, devastate, waste, sack, pillage, despoil, spoliate are comparable when they mean to lay waste or bare by acts of violence (as plundering or destroying).
Ravage implies violent, severe, and often cumulative destruction accomplished typically by depredations, invasions, raids, storms, or floods.
Devastate stresses the ruin and desolation which follow up on ravaging; it suggests eradication of buildings, of forests, and of crops by or as if by demolition or burning.
Waste may be a close synonym for devastate but it tends to suggest a less complete destruction or desolation, produced more gradually or less violently.
Sack basically suggests the acts of a victorious army entering a town that has been captured and stripping it of all its possessions of value by looting or destruction.
The term may be extended to other than military activity but consistently retains the notion of stripping of valuables and usually of destruction.
Pillage stresses ruthless plundering such as is characteristic of an invading or victorious army, but it carries a weaker implication of devastation than sack .
In nonmilitary use pillage still implies ruthlessness but it carries a stronger implication of appropriation to oneself of something that belongs to another (as by fleecing, plagiarizing, or robbing).
Despoil, like sack, implies a stripping of valuables, but it does not so often refer to a violent ransacking for booty; it more often suggests a pillaging, sometimes under a guise of legality, or a heedless or inadvertent destruction.
Spoliate is chiefly a legal term; in its meaning it comes close to despoil and is particularly applicable to destruction inflicted on a neutral, a noncombatant, or a victim of piracy or, in more general use, when the gaining of spoils by means of exactions, graft, or various venal practices is suggested.