14 of the most modern tanks would do Ukraine some good, but that is not enough to win. Estimates are that victory would require on the order of 100 tanks.

Tanks are far from invulnerable in battle, even though rifle fire bounces off them. 14 tanks, even if they are superior to the enemy's tanks, will not last long if they fight day after day. If in a large battle the Putin forces lose 50 tanks and Ukraine loses 10, we would say that the battle went Ukraine's way, but at the strategic level it would be a defeat for Ukraine. It would put an end to Ukraine's attacking with tanks.