We present a novel all-fiber UHRP source based on ultrafast pulse-stimulated dissipative four-wave mixing (FWM). By injecting an ultrafast seed pulse into a dissipative ring cavity equipped with a spectral shaper, a comb-like nonlinear response is generated. The high peak power of the seed pulse reaches the FWM threshold, stimulating a 0.275 THz pulse with an output power of 0.5 watt. The gain and spectral shaper in the fiber ring cavity form a dissipative system that modifies the initial field both temporally and spectrally, ensuring UHRP stability even after the pulse is turned off.