thoroughgoing

1. Very thorough; complete: thoroughgoing research.
2. Unmitigated; unqualified: a thoroughgoing villain.

adjective

1. Covering all aspects with painstaking accuracy: all-out, complete, exhaustive, full-dress, intensive, thorough, thoroughpaced. See big/small/amount, careful/careless.
2. Completely such, without qualification or exception: absolute, all-out, arrant, complete, consummate, crashing, damned, dead, downright, flat, out-and-out, outright, perfect, plain, pure, sheer², thorough, total, unbounded, unequivocal, unlimited, unmitigated, unqualified, unrelieved, unreserved, utter². Informal flat-out, positive. Chiefly British blooming. See big/small/amount, limited/unlimited.

The adjective has 2 meanings:

Meaning #1: very thorough; exhaustively complete
  Synonyms: exhaustive, thorough

Meaning #2: without qualification; used informally as (often pejorative) intensifiers
  Synonyms: arrant, complete, consummate, double-dyed, everlasting, gross, perfect, pure, sodding, stark, staring, utter