**Core Concept**
The question is testing the hypotensive effect of antipsychotic drugs, which is a significant side effect in some patients. The hypotensive effect is primarily mediated by the blockade of alpha-1 adrenergic receptors, leading to vasodilation and a decrease in blood pressure.

**Why the Correct Answer is Right**
The correct antipsychotic drug with a maximum hypotensive effect is **Clozapine**. Clozapine is a second-generation antipsychotic that has a high affinity for alpha-1 adrenergic receptors, which are responsible for causing vasoconstriction. By blocking these receptors, Clozapine leads to vasodilation and a significant decrease in blood pressure. This is particularly concerning in patients with cardiovascular disease.

**Why Each Wrong Option is Incorrect**
**Option A:** Haloperidol is a first-generation antipsychotic that can cause hypotension, but its effect is not as pronounced as Clozapine's. Haloperidol primarily blocks dopamine receptors, which is responsible for its antipsychotic effects.
**Option B:** Olanzapine is a second-generation antipsychotic that can cause weight gain and metabolic side effects, but it does not have a significant hypotensive effect compared to Clozapine.
**Option C:** Risperidone is another second-generation antipsychotic that can cause hypotension, but its effect is not as pronounced as Clozapine's. Risperidone has a higher affinity for serotonin receptors, which contributes to its antipsychotic effects.

**Clinical Pearl / High-Yield Fact**
When prescribing antipsychotics, it is essential to monitor patients for hypotension, particularly in those with cardiovascular disease. This can be done by regularly checking blood pressure and adjusting the dose or switching to a different antipsychotic if necessary.

**Correct Answer: D. Clozapine**