obsessive

Etymology

obsess + -ive

adj

1. Prone to cause obsession.
   The idea is too tempting, it's obsessive.
2. Having one thought or pursuing one activity to the absolute or nearly absolute exclusion of all others.
   Hardcore fans' obsessive behavior may take over their lives.
3. Excessive, as results from obsession.
   A workaholic's obsessive zeal may lead to success or burnout.
   Yes, there were instances of grandstanding and obsessive behaviour, but many were concealed at the time to help protect an aggressively peddled narrative of [Oscar] Pistorius the paragon, the emblem, the trailblazer. 21 October 2014, Oliver Brown, “Oscar Pistorius jailed for five years – sport afforded no protection against his tragic fallibilities: Bladerunner's punishment for killing Reeva Steenkamp is but a frippery when set against the burden that her bereft parents, June and Barry, must carry [print version: No room for sentimentality in this tragedy, 13 September 2014, p. S22]”, in The Daily Telegraph (Sport)

noun

1. A person who is obsessed, who has an obsession.