half-witted russian

• юро́дивый

  holy fool, yurodivy, fool for Christ

  foolish, cracked, half-witted, eccentric

• полоу́мный

  half-witted, crazy

• чумовой

  awesome, cool, terrific, amazing

  crazy, nuts, half-witted, out of one's mind

  plague victim, plague-stricken person

  plague (attributive), pestilential

• недоде́ланный

  unfinished, incomplete, half-done

  half-baked, half-witted, defective, stupid

• придуркова́тый

  daft, silly, half-witted, doltish