Systematic variation of the core pre-disruption electron temperature (Te) from 1 to 12 keV using an internal transport barrier scenario reveals a dramatic increase in the production of ‘seed’ runaway electrons (REs), ultimately accessing near-complete conversion of the pre-disruption current into sub-MeV RE current. Injected Ar pellets are observed to ablate more intensely and promptly as Te rises, and the thermal quench (TQ) is observed to shorten with increasing Te. At high Te, observed pellet ablation is far beyond expectations from thermal ablation models. Kinetic modeling of seed RE production in these discharges via the ‘hot-tail’ mechanism is performed, with good agreement found within the uncertainties in the deposited Ar profile. Modeling self-consistently treats the plasma cooling via radiation, the induced electric field, and the formation of the seed RE. Due to the combined effect of the inherent dependence of hot-tail RE seeding on Te together with the shorter TQ, modeling recovers the progression towards near-complete conversion of the pre-disruption current to RE current as Te rises. At the very highest Te (≈ 12 keV), 100% conversion of the thermal current to runaway current is found. The energy of this RE beam is inferred to be sub-MeV as it does not emit MeV hard X-rays (HXRs). Measurement of the HXR spectrum during the early current quench (CQ) reveals a trend of decreasing energy with increasing pre-disruption Te, though this cannot be conclusively isolated to variations in the RE seed as opposed to later acceleration during the CQ phase. These measurements demonstrate novel TQ dynamics as Te is varied and illustrate the practical limitation of considering RE seed formation without considering the inter-related dependencies of thermal and RE-induced pellet ablation, radiative energy loss, and resultant variations of the TQ duration. Positively, the high Te scenario in DIII-D produces REs so prodigiously that it can serve as a meaningful new testbed for demonstrating RE avoidance techniques. This material is based upon work supported by the Department of Energy under Award Number(s) DE-FC02-04ER54698.