Pups - I thought New Order were boring in concert in '87 but I wouldn't list them among my worst. It's still New Order!
I've been mulling this over for a day now and can't really come up with anything from back in my early concertgoing days. So, I'll rely on examples from the past decade:
1. Sisters of Mercy, club B1 Maximum, Moscow, 2009
One of my favorite bands of all time but this show was quite possibly the worst sound and mixing I have ever heard in a supposedly-professional concert venue. Funny thing is I'd seen them 2 years earlier in the same venue and loved it.
2. Sex Pistols, Luzhniki arena, Moscow, 2007 and/or Exit Festival, Novy Sad, Serbia 2007
They should have never toured. I mean I loved seeing them, but if I'm honest with myself they really sucked. Johnny Lydon singing an interlude about down with the USA and praise Islam had to be the lowlight of the latter appearance (he obviously confused Serbia and Bosnia. The Serbs were not amused)
Black Eyed Peas, Vasilevsky Spusk (adjacent to Red Sq), Moscow, 2006
I actually didn't pay to get into this show, thank goodness. I sat near my office across the river and enjoyed, from afar, Tatu (surprisingly good live) and Shakira (likewise). In between, I was bored to death by the Peas. Not my style anyway, but they are horrendous live.
4. Faithless Sound System, Expocenter, Moscow, 2010
I've seen the full Faithless show 3 times and included the Berlin one in my best concerts. I think they're great. Which is why I can not understand why they went on tour with this half-baked, half-produced shadow of themselves. I heard tickets to their show in Moscow last week (sadly, canceled as Maxi is sick) were selling slowly as a result of the fallout from this show and people not realizing what the difference is. Way to kill a brand.
5. Chemical Brothers, B1 Maximum, Moscow, 2007
Similar to Faithless above. Billed as some kind of live show. In reality, one of them DJed a set of their own songs while the other one went around doing jack all with racks of effects and crap positioned around them. I've heard they have another, full version of their show. I'd like to see it. This one was unbearable such that I left early. And that's a rarity for me if I paid for a ticket.