とてつもない (translations)→ extraordinary greatly numerous stupendous thundering unconscionable wildest
空想的な (translations)→ fantastical utopian
実行不可能な (translations)→ impracticable infeasible unfeasible unperformable unworkable
突拍子もない (translations)→ absurd extravagant insane mad outlandish outrageous preposterous remote unexpected wild
非現実的な (translations)→ celluloid pie-in-the-sky unrealistic