I have been taught to fear large positions. However that fear is missed place, because of all the stocks in the world someone owns them all. Large positions are to be feared when they are accumulated without a plan, or the plan has been abandoned. They should not be feared if they serve a purpose of the plan, and will be exited according to the plan.
Therefore only fear large positions when they were acquired by fear or desire. When they are acquired to a well tested plan, then there's no need to fear negative consequences or desire positive results, because both will take care of itself according to the plan.