| mercilessness(noun, ruthlessness, pitilessness, relentlessness) |
| severity |
| stubbornness(noun, state, quality, resist, perseverance) |
| adamancy(perseverance, obstinacy, stubbornness, inflexibility, rigor) |
| bullheadedness(perseverance, obstinacy, stubbornness, inflexibility, rigor) |
| call(need, essential, requirement, prerequisite, essentiality) |
| cause(need, essential, requirement, prerequisite, essentiality) |
| claim(need, essential, requirement, prerequisite, essentiality) |
| cold-bloodedness(noun, ruthlessness, pitilessness, mercilessness, relentlessness) |
| compulsion(need, essential, requirement, prerequisite, essentiality) |
| contumacy(perseverance, obstinacy, stubbornness, inflexibility, rigor) |
| demand(need, essential, requirement, prerequisite, essentiality) |
| desideratum(need, essential, requirement, prerequisite, essentiality) |
| doggedness(perseverance, obstinacy, stubbornness, inflexibility, rigor) |
| duress(need, essential, requirement, prerequisite, essentiality) |
| essence(need, essential, requirement, prerequisite, essentiality) |
| essential(need, requirement, prerequisite, essentiality) |
| essentiality(need, essential, requirement, prerequisite) |
| exaction(need, essential, requirement, prerequisite, essentiality) |
| exigency(noun, need, essential, requirement, prerequisite) |