What is the most dangerous substance in the universe?

 Let's forget about alien invasions or giant meteors rushing towards Earth or into our Solar System. There is something much more dangerous in space and it is called as Strange Matter. How is this matter actually formed in the Universe?

After the end of the life of a star, it burst and collapse under its own gravity and forms a Neutron Star (if it isn't massive enough to form a Blackhole). If the Neutron star collapses further and forms a quark star which is even smaller and denser, the pressure inside the quark star gets stronger. Things like Strange Quarks appear in its core and if they are numerous enough, they can create strange matter.

Strange matter is so stable that it is impossible to destruct and it can exist anywhere in the Universe. Also, this matter is contagious. This matter would be able to eat anything that interacts with it. Even if it is a star or planet or moon it doesn't matter, soon it touches will convert to strange matter itself. The only thing which doesn't convert is a Blackhole and practically it is not possible to toss the strange matter into a black hole.