When we first meet Neville Longbottom in the Harry Potter books, it's clear that he isn't that bright or great with his wand and magic. He constantly forgets items, manages to make a mess out of spells and potions, and is perceived as someone who is on the edge of being a squib. However, an old theory going viral on Imgur suggests that it's not Neville's fault at all, but rather his wand.
The theory, originally posted in 2004 by Soggy Old Coot on the Harry Potter Theory blogspot, explores the background of Neville's wand. As we all know, the wand chooses the wizard, and if you don't win a wand or buy a new one, it won't respond to the new owner in the proper manner. These laws of wands apply to Neville as well. His wand isn't his own, but his father's, meaning his trouble with magic might be because of this law of wands.
The story about Neville and his wand goes on further to connect it to Neville living under his father's shadow. No one thinks he's as good as his dad, and people take great pains to remind him of it. In Harry Potter and the Order of the Phoenix, Neville says, "Gran's always telling Professor Marchbanks I'm not as good as my dad . . . " Of course, later in the book, Neville's wand breaks in the Department of Mysteries, and he starts to become more apt at using his new wand that chose him.
All of this means that Neville is definitely capable of magic and using a wand correctly. "Hence, it is only logical to assume that in ideal conditions, Neville is just as talented as Harry," writes Soggy Old Coot. "We have proof of this in that every instance in which Neville has demonstrated his potential or existing abilities has been in relation to Defense Against the Dark Arts, excepting his talents with herbology, which match those of Harry's at athletics." The books after Harry Potter and the Order of the Phoenix go on to show this, especially in Harry Potter and the Deathly Hallows, where Neville manages to help win the war and make Voldemort vulnerable by killing Nagini.
Oh Neville, you're the wizard we should've had more faith in!