Collision-resistance is a stronger requirement because it directly implies (second) pre-image resistance. This is because a pre-image attack is essentially a collision attack in which one of the collision pair's hash values is fixed, and could have well been chosen by the attacker itself.

The more intuitive explanation is collision-resistance refers to the general case, whereas (second) pre-image resistance considers specific hash values (or inputs). It could be, for instance, that particular hash values are easier to invert than others; with collision-resistance, they are hard to invert in general.

Collision-resistance is a stronger requirement because it directly implies second-preimage resistance. This is because a second-preimage attack is essentially a collision attack in which one of the collision pair's hash values is fixed and a corresponding input is known, and could have well been chosen by the attacker itself.

The more intuitive explanation is collision-resistance refers to the general case, whereas second-preimage resistance considers specific input values. It could be, for instance, that the hash values of a particular subset of inputs are easier to invert than others; with collision-resistance, they are hard to invert in general.