Incapable of being surmounted or overcome.

अभेद्य

English Usage: They found themselves in an unsurmountable situation.

Hindi Usage: उन्हें एक अभेद्य स्थिति में पाया।

Something that cannot be overcome or conquered.

अविजेयता

English Usage: The challenges he faced felt overwhelmingly unsurmountable.

Hindi Usage: जिन चुनौतियों का उन्होंने सामना किया, वे अत्यधिक अविजेयता से भरपूर थीं।