Question

how many infinity stones did thanos need to destroy half of the universe

Answer 1

Thanos needs 6 infinity stones altogether to destroy half of the world. Space stone (blue), Power stone (purple), Reality Stone ( Red) Mind Stone (yellow) Time Stone ( green) and Soul Stone ( colour not known yet).

Answer 2

In the Hollywood movie Avenger's War, Thanos is a purple alien who wants to destroy half of the universe by joining all the 6 Infinity Stones together.

Those 6 Infinity Stones are -

1. Space stone which is blue in colour.
2. Reality stone which is red in colour.
3. Power stone which is purple in colour.
4. Mind stone which is yellow in colour.
5. Time stone which is green in colour.
6. Soul stone which is colourless.