El Muerto

Well, I've never heard of him but a quick google for "El Muerto DC Comics" gave this answer from the DC message boards:

El Muerto, is Pablo Valdez from Mexico City.

1st appearance in Superman Annual 12 from 2000.

Supernatural powers (impervious/undead). Part of an ignored mexican superteam.

from a blurb in wikipedia El Muerto is an undead luchador who has limited super strength, speed and mystical abilities

i also checked up on it and came up with this

from superman homepage
In Mexico City traffic is at a standstill, due to a small girl standing in the middle of the road, her eyes glowing... Three heroes, Iman, Acrata, and El Muerto; arrive on the scene.
Back in Metropolis, Lois talks to Clark, who is currently in Mexico covering a story. Clark has to leave suddenly to assist the trio of heroes. Inside Mexico's World Trade Center, the three rush to try and save the people from the collapsing building. They momentarily subdue the girl, but then Superman comes to their rescue. He approaches the girl, but she attacks him with magic. The other three stop her and teleport away with the unconscious Man of Steel, leaving the girl alone. Atop the roof, the four review the battle and Iman's computer recognizes the symbol that the little girl was wearing. Acrata says that she knows what it means, but then teleports away. The remaining three visit a scientist to learn what it means instead. He identifies it as an ancient symbol associated with a nearby temple. The three leave.

Inside of Duran's stronghold, Acrata finds the girl sleeping. She touches her and the small girl screams, bringing guards running. EL Muerto breaks through the wall to save Acrata. The other two fly in as well, but the three novices are quickly subdued, and Duran uses magic to stop Superman. The four are thrown in a cell. Inside they talk about their origins, and El Muerto tells why he hates Superman. Superman apologizes, and then Iman finds his skeleton key. In the streets, Duran rampages, using a giant fiery claw to destroy the streets. Acrata grabs Duran's pendant, but that doesn't stop the fire. They need a "visitor from the stars" to stop the evil girl. They realize that the visitor is Superman. Acrata summons the ancient god, and Superman's body is taken over. The god-Superman stops the fire creature, before the pendant shatters and the god vanishes. Having triumphed over evil, Superman returns home to his parents' house for a nice meal.

"Special Report: Justice Across the Border"

A reporter interviews people on the street about the Mexican heroes, and visits the scientist to learn some of Mexico's folklore. He also interviews Iman, and talks to Clark Kent on the street. Suddenly, the small girl attacks again. The reporter is almost killed, but the three heroes save him. However, during the fight a falling statue flattens him. The End.

this is the cover of the issue with him on it
www.fortunecity.com/tattooine/asimov/20/sann12.jpg
hes the one on the bottom left hand corner with the hangman looking mask


and also I found out that he made his last appearance in Infinite Crisis six see?

It was part of the EARTH DC (I think) theme that ran through the 2000 annuals to give a more diverse range of characters from all around the world. Others introduced have faded out into obscurity.