Select row by max of a column Pandas Python

Question

I've grouped my dataframe by two variables, and know I want to select one single row for each Client ID by the max of Var1:

Start

Client ID  Channel   Var1
1              C      100
1              A      30
2              B      55
2              C      45

Output expected:

Client ID  Channel   Var1
1              C      100
2              B      55

How can I achieve this? I've tried with df.loc[df.groupby(['Client ID','Channel'], as_index=False)['Var1'].idxmax()], but it's not working

Thanks!