The "Power" of the executive branch is through its police forces; police, marshals, sheriff's, army, navy, air-force, etc.
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Separation of power is the model. This is what balances power between the executive and legislative branch of government.
The statement, "The parliamentary form of government gives most of the power of government to the executive" (that is, to the executive branch of the government), is in fact generally false. While an executive branch of a parliamentary system may in fact have tremendous freedom to act politically as its particular genius dictates, it nevertheless receives legitimacy from the legislative branch of the government, which retains the power to revoke the power of the executive branch by formal schedule, in identifiable emergency-situations, or otherwise.
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Judicial Power, Executive Power, and Legislative Power
The other arms of government provide check for executive power. The legislature which makes laws and the judiciary which interprets the law provide a check for executive power.
The legislative branch makes (enacts) the laws. The judicial branch interprets the laws. The executive branch enforces the laws.