Hi,
There are 2 ways to do this:

a: Only see underperforming agents:
1. Drag and drop Agents and performance measure to Axis and Values respectively.

2. Drag and drop performance measure to filters and define threshold (screenshot below).

3. This will filter your chart or table to only values which are below threshold defined by user.

b. See both overperforming and underperforming agents with visual line and conditional formatting:
1. Drag and drop Agents and performance measure to Axis and Values, respectively.
2. Go to ‘customization’ and select analysis lines.

3. Add new visual line. Select the custom line and value for threshold. Rest of the options can be configured as per used need line data labels and number formatting. Screenshot below:

4. Now go to Series tab and click on ” Add new rule”

• Set your conditions if value is less than threshold value to be coloured as red
• Add another new rule if value is greater than threshold value to be coloured as green
• 
• This way you will be clearly able to see the over and underperforming agents.
  

  Please let us know if this suffices for your requirement. If not, kindly add a comment so we can discuss further.