Beauty was a quality that made lifeforms appreciate things. The adjectival form was beautiful.
Daleks[]
It was popularly believed that the Daleks did not have a concept of beauty, (WC: Planet of the Mechonoids) a statement that even the Dalek Time Controller agreed with. (AUDIO: Master of the Daleks) However the Daleks considered hatred to be beautiful. (TV: Asylum of the Daleks)
In the early days of the Dalek Empire, a rebel Dalek, through an accident in its manufacture, had human-like qualities, including the ability to appreciate beauty. It tried to teach other Daleks that beauty had to be preserved and was a strength. The Dalek Emperor reminded them beauty was not eternal or a strength and had the 'diseased' Dalek exterminated, decreeing that beauty was for human beings and human beings were to be destroyed. (COMIC: Shadow of Humanity)
Prior to the Last Great Time War, the Emperor of the Restoration however declared that the Dalek Prime Strategist's deception of the Mechanoids and the Entity as "beautiful". (WC: Day of Reckoning)
Rusty, once a standard Dalek drone, left adrift after a battle, witnessed the birth of a star. Claiming to have "[seen] beauty", Rusty turned on its own kind out of a desire to protect beautiful things. It later transpired that his mindset was due to a leak in his power cells deactivating his cortex vault. After the leak was repaired and Rusty reverted to a standard Dalek mindset, Clara Oswald convinced the Twelfth Doctor that Rusty could be made good. After the cortex vault was deactivated again, the Doctor attempted to show Rusty the beauty of the universe only for the Dalek to latch onto the Doctor's hatred for the Daleks. In the aftermath, Rusty turned on his own kind. (TV: Into the Dalek) By one account of Rusty's life, he was brought before the ruling Dalek Council and exiled to the Dalek Asylum as they found his hatred too beautiful to extinguish. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)
When the Eleventh Doctor was to be sent into the Dalek Asylum, the Prime Minister of the Daleks explained to the Doctor that they had not exterminated their brethren due to feeling that extinguishing such "divine hatred" went against their concept of beauty. (TV: Asylum of the Daleks)
Others[]
Chip considered Cassandra O'Brien.Δ17 in Rose Tyler's body to be beautiful. (TV: New Earth)
The Eleventh Doctor thought that the Elysium was beautiful. (PROSE: Hello!)
Jenny Flint thought that the Doctor's time stream was beautiful. (TV: The Name of the Doctor)
Upon his deathbed, Davros regarded the reborn Skaro as beautiful. (TV: The Witch's Familiar)
At the end of the universe, Me considered the death of the stars to be both sad and beautiful, describing Clara Oswald's death in the same manner. (TV: Hell Bent)
The Fourteenth Doctor considered his recent regeneration on a cliff to be "beautiful". (PROSE: A Letter from the Doctor [+]Paul Lang, Doctor Who The Official Annual 2024 (Penguin Group, 2023). Page 6.)