According to the Pareto Criterion, a movement from state A to state B is desirable:

if all agents are at least as well off in B as they were in A and at least one of them is better off.

if all agents are at least as well off in B as they were in A and no one is better off.

if the agent with lower welfare are found to improve their welfare in B in comparison to A even when those with higher level of welfare in A are found to witness decline in welfare.

if in B all the agents are having lower difference in their level of utilities