Tricky

Let's get to the point right away - there is NO WAY ON EARTH that you can look good when performing with Beyonce. OK, Jay-Z can do it, but he's rapping with her, not singing with her so it's something else.

For her Glastonbury 2011 performance Beyonce introduced us to her personal 'friend' Tricky (stop laughing! It's probably a real name......)
He comes in pushing a microphone stand like a zimmer frame. Seriously, if you've not seen it yet, go and have a look at the video! That must have worn him out because he then procedes to breath heavily into the mic for a bit, before trying to sing a lyric, fails, and is consoled by his duet partner.
In this 'performance' he is definitely the Pussycat Dolls to Beyonce's Nicole Scherzinger. To make matters worse for poor ol' Tricky, Sean Paul is STILL being played over the top of the track.

This poor guy looks to be a contest winner who is promptly disposed of!
Still, good to know that it doesn't matter how talentless you might be, as long as you've got famous friends, you're gonna be fine :)