Given that Lord Voldemort’s rage and terror can be triggered by the mere mention of Albus Dumbledore’s name, it’s safe to assume that he’s the most powerful magic-user in Harry Potter. As a result, Dumbledore is likely to be familiar with almost every spell in the franchise, if not all of them.

Expulso is too fiery and loud for Dumbledore’s understated style.

Expulso’s explosions are instrumental in melee fights where the user’s goal is to flee. The spell summons a bomb-like burst of energy capable of destroying most household items as well as injuring anyone caught in its blast radius.

His comedic value overshadows Engorgio’s combat ability.

Miranda Goshawk warns her readers against “over-enthusiastic casting,” emphasizing the importance of learning both Engorgio and Reducio at the same time.

Dumbledore Knows Much Better Magic Than Relashio’s Simplistic & Violent Magic

The Revulsion Jinx, or Relashio, causes a target to “relinquish its hold on another object.” It is Harry Potter’s only spell that can be used both on land and underwater.

Obliviate revokes a person’s right to free thought and expression.

Obliviate obliterates a person’s memories with incredible precision, and the caster has control over the spell’s effectiveness. Because the International Statute of Secrecy requires that the Wizarding World remain invisible and intangible to interference, the Memory Charm comes in handy when Muggles or No-majes come into contact with magic.

The Malevolence Fiendfyre Radiates Outweighs Its Theoretical Benefits

Vincent Crabbe is most likely the last person capable of creating Fiendfyre. After being cast, a dark conflagration develops consciousness.

Conferring Is Unwieldy & Overly Destructive

Conferring is related to Expulso and Reducto, but it is far more dangerous. In Bathilda Bagshot’s room, Hermione casts the spell, which “bounces from floor to ceiling,” destroying Harry’s beloved wand in the process.

Densaugeo Is Too Silly For Most Adults Even To Consider Casting

Densaugeo is a minor hex that Draco casts on Harry, but it misses its mark and hits Hermione instead. As a result, her “already larger than average” front teeth protrude downwards like the teeth of some grotesque mutant beaver.

The Caster of the Horcrux-Making Spell Must Murder

Horcrux magic is a dangerous and challenging undertaking for anyone. Even without the soul-fragmentation process required for the spell to work.

Although Silencio is technically useful, Dumbledore prefers the hustle and bustle of Hogwarts.

As Headmaster, one might expect Dumbledore to have used the Silencing Charm at some point during his career. Perhaps to reduce the decibel level in the Great Hall. 

The Unforgivable Curses destroy the agency of their targets, which Dumbledore will not tolerate.

Dumbledore can’t bear the idea of using the Unforgivable Curses. Partly because of his sister Ariana’s unintentional death. But mainly because he’d never willingly destroyed a human’s agency.