Overturn, upset, capsize, overthrow, subvert are comparable because they carry a common basic meaning-to cause to fall, or, intransitively, to fall, from the normal or proper position. Otherwise they vary widely in their applications and implications.
Overturn is usually the least explicit in its additional implications; sometimes it implies a turning upside down, but more often it implies a turning on the side so that the thing affected lies flat on the ground.
Sometimes, especially when the thing affected is a state, an institution, or something which has been built up or become established, the term also implies a breaking down and consequently a ruining or destroying.
Upset is the familiar term and implies especially a loss of balance, sometimes physical, sometimes mental, often emotional (for this sense of upset see DISCOMPOSE ) as the result of some external or internal cause or agency.
But upset more often than overturn is used to imply the abolition of something established or the demolishing of something built up.
Capsize is specifically applicable to the upsetting or overturning of a boat; in more general use it usually suggests a complete overturning and is sometimes employed in an extended sense to imply a turning, especially a sudden turning, upside down or topsy-turvy, not only physically, but mentally or morally.
Overthrow (see also CONQUER ) carries a stronger implication of the exercise of force, violence, or strategy than any of the preceding terms; it often also implies consequent defeat, destruction, or ruin.
Subvert implies an overturning or overthrowing of something held to be of intrinsic value (as a form of government, or morality, or religion) by undermining its supports or weakening its foundations; often it suggests the operation of insidious or corrupting influences.