Sung to Jingle Bells (Start with the "Dashing through the snow" verse). This is my favorite, especially the eggnog stanza.

Avengers Holiday

Zooming through the air
Blasting all the way
Iron Man flies past
As teammates join the fray.

Captain throws his shield
While guns and arrows flash
Odin's son rains lightning down
And verdant knuckles smash

Oh,
"What the hell?" bad guys yell
As they run away
They'll be sorry they disturbed
Avengers' holiday

"What the hell?" bad guys yell
As they run away
They'll be sorry they disturbed
Avengers' holiday

Eggnog's getting warm
Turkey's getting cold
Supervillain schemes
Are getting really old.

Yule is not the time
To make Avengers mad
So like a well-oiled team they strike
And make the crooks look sad

Oh,
"What the hell?" bad guys yell
As they run away
They'll be sorry they disturbed
Avenger's holiday

"What the hell?" bad guys yell
As they run away
They'll be sorry they disturbed
Avengers' holiday

Captain lands a punch
To knock a monster down
Hulk takes two or three
And slams them on the ground

Clint and Widow sneak
To catch the boss alone
Then they wrap up the Christmas crime
And tie it with a bow

Oh,
"What the hell?" bad guys yell
As they run away
They'll be sorry they disturbed
Avengers' holiday

"What the hell?" bad guys yell
As they run away
They'll be sorry they disturbed
Avengers' holiday