That weakens, in various senses of the verb.

That debilitates; weakening, enfeebling.

Tending to debilitate; causing debilitation.

Medicine. Resulting in or characterized by weakness or debility; spec. designating fevers which have a marked debilitating effect. Cf. adynamic, adj.…

That enervates, in the various senses of the verb.

That prostrates or casts down; (chiefly figurative) overpowering, exhausting, enervating.

Medicine. = adynamic, adj. 1a.

Debilitating.