There are several tropes of Lancelot Du Lac from The Magic Knight, which appear in the website Tv Tropes

Affectionate Nicknames: He is commonly called "Lance" instead of his real name by most of his friends and family, he is also called "Angelic Child" by his mother.

Amazingly Embarrassing Parents: Lancelot knows his mother means well, but can sometimes be embarrassing when it comes to her Angelic Child.

Ancestral Weapon: He wields one of his ancestor Sir Lancelot's famous sword, the demon sword, Secace.

Arranged Marriage: Lancelot's grandmother had arranged for him to marry Xenovia when both graduated and the moment that Lancelot officially becomes the next head of the Du Lac Family.

Awesome McCool Name: Lancelot inherited the same name as his ancestor, Sir Lancelot, the well-known and the most respected Knight of his era. 

Back-to-Back Badasses: When a powerful Angel-Human Hybrid teams up with his equally powerful childhood friend or ally you don't want to be their enemy.

Badass Family: The Du Lac Family, a family of skilled knights who've fought against Devils and Monsters for several years. Examples: His father who is generally known as the "True War God", his grandmother who is feared and respected by most as the "Crimson War Goddess".

Battle Aura: As a user of Aura.

Berserk Button: He would normally like to keep his laidback demeanor, but when his family or friends are in danger, then you are most likely screwed.

Big Brother Instincts: His main motivation when fighting is to protect those who he views as his younger siblings, this includes the children in the Orphanage, along with Asia and Gasper.

Big Fancy House: In Kuoh Town, Lancelot formerly lived in the normal two-story house that he lived in since he was a child. After the alterations done by both his families, it went through some minor changes. 

Bishōnen: Lancelot is the child of a handsome Knight and a beautiful Angel, as such he inherited more than just their strong genes.

Break the Badass: Despite all of the feats that Lancelot achieved since childhood, along with the power that he gained as a seventeen-year-old. As of now, he's still incapable of fighting against his grandfather who is known as and feared as the 'Mage God', the one who personally murdered several highly skilled Knights, the six Paladins, and the Head Paladin. So in short...he has his work cut out of him.

Brilliant but Lazy: Lancelot prefers to sleep or take a short nap on the school roof or fields, despite being considered to be the 'Strongest Knight of his Generation' and one of the smartest people who're his age. Sometimes even while on a mission, Lancelot would take a short nap before doing anything else. 

Chick Magnet: A natural trait of a Hero is attracting a large number of women, especially when you're attending a school full of hormonal teenage girls. 

Childhood Friends: Lance, Issei, and Irina are as close as close can be. They are childhood friends who made a promise to always be there for each other. 

Childhood Friend Romance: Both Lancelot and Irina, are both childhood friends and share a mutual love for each other.

Child Prodigy: Lancelot is a well-known child prodigy of the Du Lac and Ambrosius Family, and is considered to be a genius by the members of his family.

the  Ambrosius Family, who believes training and experience can allow him to truly show those traits to the fullest.

Cool Sword: He was shocked to find his ancestors' Demon Sword, to suddenly end up in his possession. And when it can cut through space it makes it cooler.

Dad the Veteran: His father is a Knight who's been fighting against Demons, Devils and other creatures of darkness since he was a child.

Dark and Troubled Past: A child who grew up with a deranged Magician doesn't exactly have a childhood filled with; being dropped into a hydra pit at the age of 7, emotional abuse and mental abuse, and witnessing him murder his father along with his comrades right in front of you.

Deadly Upgrade: He already dangerous on his own without it, but when succumbing to the curse of Secace, he becomes more of a brutal fight. With the price of damaging his body.

Deadpan Snarker: Lancelot is well-known for being sarcastic, especially when it comes to an opponent he's fighting.

Demon Slaying: The usual job of a Knight of the Chivalric Order and a member of the Du Lac Family.

Family Business: As a Knight of the Du Lac family, you normally have the job of fighting against Evil.

Famous Ancestor: He's the descendant of Sir Lancelot and Merlin Ambrosius.

Fight Magnet: Being the relative of a strong Knight and a Magician, along with being the grandson of a God may sound cool. But it puts you in the middle of a war, where a terrorist organization and are trying to end the world.

First Kiss: He shared his first kiss with his childhood friend and crush since childhood, Irina. 

Friend of all Children: Lancelot has shown several times to be able to befriend children, with them seeing him as their older brother.

Half-Human Hybrid: The Hybrid son of his Angel mother Gabriel and his Human father Galahad.

Heroic Lineage: He's the child of a well-known Hero of the Chivalric Order, who's known as the 'True War God'.

I am not Left-Handed: This is used several times with Lance, whenever he's forced to use War God Mode, his physical abilities are increased greater than they were before.

Like Father, Like Son: Like his father, Lancelot also carries the potential to become stronger than he is now, but also inherited his laidback mood and his sleeping habit.

Magic Knight: Knight + Magician= Absolute Awesomeness

Missing Mom: After having his memory wiped by his grandfather, he couldn't remember his mother nor could she come near him for almost ten years.

Named after someone Famous: Lance's full name is Lancelot Du Lac, after his ancestor who shared the same name.

New Transfer Student: A new transfer at Kuoh Academy, after finishing his training.

Oblivious to Love/Clueless Chick Magnet: A typical trait of all male Heroes, he attracts several women, but he can be oblivious to that fact.

The Cape: Lancelot doesn't want to be awarded for his achievements, he only desires to be strong enough to protect what's important to him from any threat. He'd rather live a peaceful life with his friends and family.

The Dreaded: Lancelot from the perception of many Demons, Stray Devils, and even some Vampires. As the son of the War God and Seraph, he would be someone that you wouldn't want to make an enemy. 

The Slacker: Possibly his most well-known trait of falling asleep whenever he gets the chance; whether it's before the start of a mission, on the roof of Kuoh Academy during Lance, and/or even rarer times during the middle of class.

Teen Genius: Being the descendant of a brilliant Magician comes with some other perks.

Training from Hell: He thought his training with the Chivalric Order was tough, but training with the 'Crimson War Goddess' makes it looks like child's play.

The Ace: Along with several other characters of DxD he's considered to be one of their Aces.

Unstoppable Fury: To most Lancelot may seem calmed and relaxed, but become his enemy or hurt those that he cares about, then you'll see a side of him that you wished you hadn't.