It has to be Bucharest Baneasa (BBU)!
Nothing more than a glorified bus shelter! To its credit the air side logistics seemed OK, i.e. buses to plane, steps, luggage etc.
Some people quote it as "Europe's Worst Airport".
Cluj Napoca (CLJ) isn't much better either, my boarding pass was a old one with the old flight details crossed out and written over!
However Bucharest Otopeni (OTP) whilst not perfect was acceptable, very quick on arrival. 15 minutes from plane to exit, and on departure security was very easy. The taxi touts have seem to of almost disappeared also. However it is extremely expensive, ie £2.50 for a tiny coffee! Especially when your used to paying around 60p in Bucharest!