Question: What characteristic is shared by Deadpool and Taskmaster? 

Context paragraphs:
Cherenkov radiation: Cherenkov radiation, also known as Vavilov–Cherenkov radiation (named after Sergey Vavilov and Pavel Cherenkov), is electromagnetic radiation emitted when a charged particle (such as an electron) passes through a dielectric medium at a speed greater than the phase velocity of light in that medium.  The characteristic blue glow of an underwater nuclear reactor is due to Cherenkov radiation.  It is named after Soviet scientist Pavel Alekseyevich Cherenkov, the 1958 Nobel Prize winner who was the first to detect it experimentally.  A theory of this effect was later developed within the framework of Einstein's special relativity theory by Igor Tamm and Ilya Frank, who also shared the Nobel Prize.  Cherenkov radiation had been theoretically predicted by the English polymath Oliver Heaviside in papers published in 1888–89.

Deadpool: Deadpool (Wade Winston Wilson) is a fictional antihero appearing in American comic books published by Marvel Comics.  Created by artist/writer Rob Liefeld and writer Fabian Nicieza, the character first appeared in "The New Mutants" #98 (cover-dated February 1991).  Initially Deadpool was depicted as a supervillain when he made his first appearance in "The New Mutants" and later in issues of "X-Force", but later evolved into his more recognizable antiheroic persona.  Deadpool, whose real name is Wade Wilson, is a disfigured and mentally unstable mercenary with the superhuman ability of an accelerated healing factor and physical prowess.  The character is known as the "Merc with a Mouth" because of his talkative nature and tendency to break the fourth wall, which is used by writers for humorous effect and running gags.

Idiotype: In immunology, an idiotype is a shared characteristic between a group of immunoglobulin or T cell receptor (TCR) molecules based upon the antigen binding specificity and therefore structure of their variable region.  The variable region of antigen receptors of T cells (TCRs) and B cells (immunoglobulins) contain complementarity determining regions (CDRs) with unique amino acid sequences.  They define the surface and properties of the variable region, determining the antigen specificity and therefore the idiotope of the molecule.  Immunoglobulins or TCRs with a shared idiotope are the same idiotype.  Antibody idiotype is determined by:

Slayback: Slayback is a fictional character appearing in American comic books published by Marvel Comics.  Primarily an enemy of Deadpool, the character exists within Marvel's main shared universe, known as the Marvel Universe.  Created by writer Fabian Nicieza and artist Joe Madureira, the character first appeared in "Deadpool: The Circle Chase" #1 (August 1993).

Synapomorphy: In phylogenetics, apomorphy and synapomorphy refer to derived characteristics of a clade.  Apomorphy implies a characteristic that is different from the form of an ancestor, i.e., an innovation, of use in determining membership in a clade.  Synapomorphy is a shared derived character or trait state that distinguishes a clade from other organisms.  In other words, it is an apomorphy shared by members of a monophyletic group, and thus assumed to be present in their most recent common ancestor.  The word synapomorphy, coined by German entomologist Willi Hennig, is derived from the Greek words "σύν ", "syn" = shared; "ἀπό ", "apo" = away from; and "μορφή ", "morphe" = shape.

Johnsenite-(Ce): Johnsenite-(Ce) is a very rare mineral of the eudialyte group, with formula Na(Ce,La,Sr,Ca,[])CaMnZrWSi(SiO)(SiO)(CO)O(OH,Cl).  The original formula was extended to show the presence of both the cyclic silicate groups and silicon at the M4 site, according to the nomenclature of the eudialyte group.  It is the third eudialyte-group mineral with essential tungsten (after khomyakovite and manganokhomyakovite), and second with essential rare earth elements (after zirsilite-(Ce), which is the niobium-analogue of johnsenite-(Ce)).  In fact, some niobium substitutes for tungsten in johnsenite-(Ce).  Other characteristic feature is the presence of essential carbonate group, shared with carbokentbrooksite, golyshevite, mogovidite and zirsilite-(Ce).

Europeanism: Europeanism is a term that encapsulates the norms and values that Europeans have in common, and which transcend national or state identity.  In addition to helping promote the integration of the European Union, this doctrine also provides the basis for analyses that characterise European politics, economics, and society as reflecting a shared identity.  Opponents to the idea stress that there are various differences among European groups and that the factors seen as characteristic of this shared culture do not necessarily follow its premise.

Cable &amp; Deadpool: Cable & Deadpool was a comic book series published by Marvel Comics beginning in 2004.  The title characters, Cable and Deadpool, shared the focus of the book.  The series was launched following the cancellation of the characters' previous ongoing solo series.  The book's mix of humor, action, and intricate plotting have won it a devoted fanbase.  Marvel Comics canceled the series with issue #50 to make way for a new "Deadpool" ongoing series that began on September 10, 2008, and a new Cable ongoing series that was launched in March 2008.  Cable & Deadpool were ranked #7 on Marvel.com's list of "The 10 Greatest Buddy Teams" of all time.

Callorhinchidae: The Callorhinchidae (sometimes spelled "Callorhynchidae"), or plough-nose chimaeras, are a family of marine fish containing one genus, Callorhinchus.  They are similar in form and habits to other chimaeras, but are distinguished by the presence of an elongated, flexible, fleshy snout, with a vague resemblance to a ploughshare.  The snout is used to probe the sea bottom in search of the invertebrates and small fishes on which it preys.  The remainder of the body is flat and compressed, often described as elongated.  The mouth is just under this snout and the eyes are located high on top of the head.  The usual color is black or brown, and, often a mixture between the two.  Phylogenetically, they are the oldest group of living jawed Chondrichthyes.  They possess the same cartilaginous skeleton seen in sharks but are considered holocephali to distinguish them from the shark and ray categorization.  Because of this, they provide a useful research organism for studying the early development of the jawed characteristic.  Among the Chondrichthyes genome, "Callorhinchus" has the smallest genome.  Because of this, it has been proposed to be used for entire genome sequencing to represent the cartilaginous fish class.  They are considered to resemble a cross between a shark and a ray or skate, but can be distinguished from sharks because they possess an operculum over their gill slits.  Additionally, their skin is smooth, not covered in tough scales, characteristic of the shark.  While the shark's jaw is loosely attached to the skull, the Callorhinchidae family differ in that their jaws are fused to their skulls.  Many classify the Callorhinchidae as a chimeric species due to their shared characteristics of both the sharks and rays.  They are found in muddy and sandy substrates of the ocean bottom, where they filter feed, with small shellfish making up the bulk of their diet.  They have broad flat teeth that have adapted for this type of eating habit, two pair that reside in the upper jaw and one pair in the lower jaw.  In addition to its utilization for feeding, the trunk of the Callorhinchus fish can sense movement and electric fields, allowing them to locate their prey.  They possess large pectoral fins, believed to aid in moving swiftly through the water.  They also have two dorsal fins spaced widely apart, which help identify the species in the open ocean.

Taskmaster (comics): Taskmaster (Tony Masters) is a fictional supervillain, and sometimes an antihero, who appears in American comic books published by Marvel Comics.  The character first appeared in "The Avengers" vol.  1 #195 (May 1980), and was created by David Michelinie and George Pérez.  Introduced as an enemy of the Avengers, Taskmaster went on to feature in numerous Marvel titles, most notably as an enemy/ally of Deadpool.  He is often depicted as a mercenary hired as a training instructor by various criminal organizations.  In "Taskmaster" vol.  2 #3 (2011), the character was revealed to be a sleeper agent of S.H.I.E.L.D. planted by Nick Fury to gather intelligence in the criminal underworld.

Supporting paragraphs: Taskmaster (comics) Deadpool
Answer: fictional supervillain, and sometimes an antihero