I'm looking for a tool that will select just these certain features (mark them in a new column or just delete all other features). It´s the highest number of "OBJECTID" for every number of "arcid".
I'd warn you against using the
OBJECTID field for anything, the values in it can change when the layer is edited. I'm guessing what you're trying to do here is find the most recent version of each feature. Using
OBJECTID for that will probably work, as long as the layer hasn't had features deleted from it.
You can use the Summary Statistics tool to find the maximum value in a field based on values in another field. In this case you would run the tool using
arcid as the CASE field and
OBJECTID as the Statistics field with MAX as the Statistics Type. I'm not sure that you can actually use the
OBJECTID field in geoprocessing like this, you may have to create a new field and copy the values in
OBJECTID to it, then use that new field as your Statistics field.