| persevering(adjective, strong, firm, determined, steady) |
| contumacious(adjective, determined, fixed, persistent, obstinate) |
| enduring(adjective, calm, cool, determined, resolute) |
| impassable(adjective, steadfast, unyielding, insuperable) |
| insuperable(adjective, steadfast, unyielding) |
| invulnerable(adjective, steadfast, unyielding) |
| iron(adjective, strong, hard, tough, resolution) |
| irresistible(adjective, strong, strength, violent, wild) |
| mighty(adjective, powerful, forceful) |
| sturdy(adjective, strong, hard, great, tough) |
| tireless(adjective, strong, firm, determined, steady) |
| uncontrollable(adjective, strong, wild, away, overwhelming) |
| unfaltering(adjective, strong, firm, determined, steady) |
| unflagging(adjective, strong, firm, determined, steady) |
| ungovernable(adjective, difficult, violent, wild, awkward) |
| unstoppable |
| unsubduable |
| untiring(adjective, determined, perseverance, persevering) |
| valiant(adjective, strong, tough, determined, vigorous) |
| diligent(adjective, resolute, tenacious) |