Abysmal

Adjective

 * 1) Pertaining to, or resembling an abyss; bottomless; unending; profound; fathomless; immeasurable.
 * 2) Extremely bad.

Thesaurus
Atlantean; Brobdingnagian; Cyclopean; Gargantuan; Herculean; Homeric; abyssal; appalling; astronomic; awful; bottomless; cavernous; colossal; deep as hell; dreadful; elephantine; enormous; epic; fathomless; gaping; giant; giantlike; gigantic; heroic; huge; illimitable; immense; infinite; jumbo; mammoth; mighty; monster; monstrous; monumental; mountainous; plumbless; plunging; prodigious; profound; soundless; stupendous; terrible; titanic; towering; tremendous; unfathomable; unfathomed; unsounded; vast; without bottom; yawning