Some 9.44 million (33.3%) watched the singing contest's results show from 8pm (+1: 198,000), with a peak of nearly 11m gripped by the show's climax which saw Henderson leave the competition to the anger of mentor Tulisa Contostavlos.
The Xtra Factor followed on ITV2 with 787k (2.8%), achieving double last week's average, and overtaking fellow spinoff I'm a Celebrity... Get Me Out of Here Now which ended up settling for 728k (5.1%) at 10.30pm.
The X Factor, on gaining half a million week-on-week, significantly closed the gap on Strictly Come Dancing which itself lost half a million.
I'm a Celebrity... Get Me Out of Here! overtook Strictly to top the Sunday night ratings battle, pulling in a huge 10.19m (38.3%) and 457k (2.7%) on ITV1 +1.
Richard Arnold's Strictly departure was seen by 9.92m (36.2%) from 7.15pm, peaking with 10.27m (37.1%) as the result was announced.
BBC One's haunted house drama The Secret of Crickley Hall made a fine start with 5.28m (18.7%) up against the muscle of ITV's I'm a Celeb.
Antiques Roadshow preceded Crickley Hall with 6.02m (21.2%), while Countryfile commanded 6.79m (28.7%) even earlier at 6.30pm.
Elsewhere, 1.98m (7.1%) watched Homeland as Channel 4 got the better of BBC Two in the 9pm hour, the latter appealing to 1.52m (4.2%) for Dragons' Den. Meanwhile, Channel 5's screening of Forgiven attracted 843k (3.9%).
Without Friday Night Dinner as competition, Harry and Paul climbed to 1.01m (4.3%) for an episode which featured a bizarre guest appearance of UKIP leader Nigel Farage.
Overall, ITV1 triumphed in primetime with 28.9% (+1: 1%), overcoming BBC One (22.9%) with ease. With 5.6% (+1: 1.1%), Channel 4 finished just above BBC Two (5.4%) to make third, while Channel 5 had just 2.8% (+1: 0.3%).
BBC Three sitcom Him and Her returned in a double bill special at 10pm, appealing to 411k (1.7%) and 491k (2.3%) as the third run kicked off.
BARB ratings data supplied by Attentional