How to drop duplicates in first column and output values in 2nd column?

I have a tab-separated CSV file like this

C1      C2
A       3
B       4
C       5
B       4
A       3

How can I get rid of duplicates in col 1 and output the values from col 2 for each unique col1 value? Example output:

3
4
5

I’ve tried awk -F 't' '{print $1}' file_name.csv | sort | uniq -c which sorts the data in the first column and ‘drops’ duplicates but this gets rid of column 2. I’m just a beginner to shell scripting so any help will do.