Steven Gerrard was Liverpool's hero with a stoppage-time penalty as the Reds marked their return to the Champions League with a win, while Arsenal endured a torrid evening against Borussia Dortmund.
Gerrard struck from the spot right at the death to hand Liverpool a 2-1 win in their Group B opener against an awkward Ludogorets Razgrad at Anfield yesterday.
Meanwhile, goals just either side of half-time by Ciro Immobile and Pierre-Emerick Aubameyang gave 2013 runners-up Dortmund a 2-0 win against Arsenal in Germany in Group D, and the hosts were unlucky not to win by more.
The evening's big winners were the reigning champions Real Madrid, who crushed Swiss title-holders Basel 5-1 in Group B, while last season's beaten finalists Atletico Madrid suffered a 3-2 defeat against Olympiakos in Greece in Group A.
Liverpool were making their first appearance in the Champions League since 2009 and were widely expected to start with a victory against Bulgarian debutants Ludogorets.
Brendan Rodgers's side laboured for long spells but when Mario Balotelli put them in front in the 82nd minute to open his Anfield account, they appeared to have the job done.
Spanish substitute Dani Abalo stunned the hosts when he equalised in the first minute of stoppage time, but there was to be another twist as Javi Manquillo was fouled inside the box, allowing Gerrard, so often a scorer of crucial late goals in the past, to convert a 93rd-minute spot-kick.
"To get the result was excellent. They showed great character to keep going," said Rodgers.
"We had signs of anxiety. We are not at the level we were at last year yet, but that will come with time."
Arsenal were torn apart by a typically high-octane Dortmund performance at the Westfalenstadion. The hosts had 15 attempts on goal in the opening half but had to wait until the 45th minute to get the breakthrough when Immobile ran 60 yards before slotting past Wojciech Szczesny.
Aubameyang then exchanged passes with Kevin Grosskreutz before rounding the goalkeeper and making it 2-0 in the 48th minute, and the Gabon striker hit the bar soon after as Arsenal lost their opening Champions League game for the first time in 11 years.
