Time ram

Time Ram is the name given to what happens if two TARDISes attempt to occupy exactly the same time and space. (DW: The Time Monster) Such an occurrence, according to the Doctor, would cause a black hole strong enough to destroy an entire universe. (DW: Time Crash)

It can be narrowly avoided by the two TARDISes materialising within each other. (DW: The Time Monster, Logopolis, Time Crash)

The Sixth Doctor performed a time ram against the remains of Iris Wildthyme's TARDIS at the center of a dimensional nexus. Local conditions limited the effects to merely eliminating some possibilities from reality, but the force was still enough to destroy the rest of Iris' TARDIS. (BFA: The Wormery)