IF and only if ABC.COLUMN2 is a (very) large column, and ABC.COLUMN1 is used by itself a lot, it might be worthwhile to keep both indexes.
You should also review sys.dm_db_index_usage_stats to see how often, and in what ways, each index is currently being used.
SQL DBA,SQL Server MVP(07, 08, 09) Prosecutor James Blackburn, in closing argument in the Fatal Vision murders trial:
If in the future, you should cry a tear, cry one for them [the murder victims]. If in the future, you should say a prayer, say one for them. And if in the future, you should light a candle, light one for them.