Consider

When right-click on any creature or pressing C when they are targetted you will get a rough estimate of their power based on their level:

This opponent is not worth your time. - 4+ levels below you

You should easily win this battle. - 1-3 levels below you

You'd be an even match for this opponent. - same level as you

This is a strong opponent. - 1-3 levels above you

You wouldn't stand a chance alone! - 4+ levels above you