insuperable (adj.)

mid-14c., "unconquerable, incapable of being surmounted," from Old French insuperable (14c.) or directly from Latin insuperabilis "that cannot be passed over, unconquerable," from in- "not, opposite of" (see in- (1)) + superabilis "that may be overcome," from superare "to overcome," from superus "one that is above," from super "over" (from PIE root *uper "over"). Figurative use from 1650s. Related: Insuperably; insuperability.