My bet would be Muay Thai. Muay Thai has highly effective techniques for controlling an opponent in the clinch. The control allows for very effective setups for striking with all 'eight' limbs, and to offset the base of the opponent. It is the latter that is most beneficial to Judo players since offsetting your opponents base is the name of their game. This allows them not only to strike effectively, enter their throws set up from the striking (think Karo Parisyan of the UFC), but also serves to keep them safe since the opponent can neither strike, nor attempt an effective take down whilst off balance (think Anderson Silva).
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