Final answer:
Succinylcholine has the fastest onset time among the options provided.
Step-by-step explanation:
The paralytic with the fastest onset time among the given options is Succinylcholine. Succinylcholine is a depolarizing neuromuscular blocking agent that acts as an agonist for acetylcholine receptors. It has a rapid onset of action and a short duration of effect, making it suitable for quick and short-term paralysis.
Vecuronium, Rocuronium, and Atracurium are all non-depolarizing neuromuscular blocking agents. These drugs have slower onset times compared to Succinylcholine but longer durations of effect. They work by blocking the action of acetylcholine at the neuromuscular junction, leading to muscle paralysis.