Definition: Uglification - deliberate creation of ugliness (as contrasted with the failure to create beauty).
Mark Rothko - Brown on Black
...with the (relative) failure to create beauty...
Thomas Kinkade Christmas greetings card:
The difference is that Kinkade's is a not-particularly-successful attempt to make a beautiful picture; while Rothko is not-even-trying to make a beautiful picture...
The difference is that Kinkade is utterly loathed by art experts, while Rothko is regarded as a godlike hero of twentieth century art.
Actually, the 'Rothko' painting above is a total fake - it is in fact a picture of some wallpaper.
A real Rothko would be something like Black Form Painting number 1:
...which is, of course, ahem, much more beautiful than the wallpaper...
In the history of art, there was an evolution from the hard job of trying to make ultimate beauty (and either succeeding or failing to some lesser-or-greater degree, like Kinkade); via trying to make something beauty-in-ugliness or not-primarily-beautiful but 'true' (maybe like some of Rembrandt's portraits of ugly people) - which is even more difficult, but possible; to uglification - deliberate making of varieties of ugliness: monotony and dullness, horror and revulsion, aggressive violence, blatant but ironic vulgarity, obscenity etc (which category pretty much all of the 'great' names of 20th century art) - which is very, very easy...
1. Artists want to avoid the shame of failure - ultimate beauty is extremely difficult to attain, but you pretty much cannot fail if you are try to create ugliness.
2. Status games - the implicit desire to imply that the art expert has insight to arcane knowledge - sees through the surface ugliness, can perceive beauty in ugliness.
3. Renders art captive to critical opinion - the artist is merely an interchangeable unit, and art is defined by critical consensus.
4. Evil. The poisoning of mortal life by the propagation of ugliness. The perplexing and subversion of the human spirit by high status consensus that black is white, two plus two makes five and viscerally-repellent ugliness is beauty such that Rothko is analogous to Vermeer -- whereas in reality they were engaged in opposite activities - as different as evil from good, Satan from Christ.
The Geographer by Johannes Vermeer