The last I witnessed was, as Dick Swiveller remarks, a 'stifler.'
Ridicule is the stifler of all energy amongst those she controls.
late 14c., "to choke, suffocate, drown," of uncertain origin, possibly an alteration of Old French estouffer "to stifle, smother," which may be from a Germanic source (cf. Old High German stopfon "to plug up, stuff"). Metaphoric sense is from 1570s. Related: Stifled; stifling.