Germany 6 Northern Ireland 1
An injury stricken Northern Ireland side were made to suffer for poking the German bear in a freezing Frankfurt on Tuesday night.
Hearts defender Michael Smith rifled home a stunning first international goal on seven minutes, however this fantastic thunderbolt only antagonised a much-changed German side who responded in fearsome fashion with a hat trick from Serge Gnabry, Leon Goretzka's double and Julian Brandt's injury time strike.
This was not how O'Neill envisaged his final ever Northern Ireland qualifying match going and Craig Cathcart and Josh Magennis will not be reviewing the game in which they won 50 caps any time soon.
But O'Neill's farewell Northern Ireland tour will rumble on to Bosnia and Herzegovina on March 26 in the one-leg Euro play-off semi-final after Wales beat Hungary 2-0 in Cardiff last night to automatically qualify for the finals and force the men in green to go away to reach the finals.
Then it could be an all-Ireland final on March 31 with the Republic playing away to Slovakia in the other semi-final.
This though was Northern Ireland heaviest defeat under O'Neill since his second game in charge (6-0) against the Netherlands seven years ago.
Just as in 2012 in Amsterdam, O'Neill was missing key players and therefore at a serious disadvantage and facing a monumental challenge before the game had even started.
Talisman defender Jonny Evans was missing through illness while the versatile Stuart Dallas, winger Gavin Whyte and Jamal Lewis were all out injured.
League One players Tom Flanagan and Jordan Thompson made their first competitive starts with full backs Shane Ferguson and Michael Smith coming into the side.
Josh Magennis retained his place as the lone striker - a thankless task.
Joachim Low made six changes from the side that beat Northern Ireland 2-0 at Windsor Park in September with Marcel Halstenberg, who scored that stunning half volley to open the scoring in Belfast, not even in the match day squad and Barcelona goalkeeper Marc-Andre Ter Stegan taking the place of Manuel Neuer between the post.
In a breathtaking opening 20 minutes, Smith scored the greatest goal of his career when he connected magically with a thunderous shot on seven minutes from 26 yards out to beat the despairing dive of Ter Stegen.
The Germans were startled, their fans inside the vast Commerzbank Arena silenced while the Northern Ireland supporters, huge in number behind Ter Stegen's goal, were creating all the noise.
Bailey Peacock-Farrell made a magnificent point blank save from Gnabry after being beautifully played through and evading the offside trap. Then, Manchester City's Ilkay Gundogan struck the post with a header after delicate cross from skipper Toni Kroos.
Northern Ireland, while pushed back, were playing without fear and Paddy McNair threatened the German goal before Cathcart had to make a decent block from a Brandt shot and then the Watford man was fortunate his keeper came to his aid after diverting a Hector cross goalwards. With the pressure mounting, Northern Ireland living dangerously, Gnabry scored a magnificent equaliser on 19 minutes. The former Arsenal striker received a pull back from Jonas Hector, and with his back to goal and he managed to turn and shoot into the top corner, evading a challenge from Cathcart.
The men in green were showing plenty of endeavour but the Germans were relentless with their slick, integrate passing and free-flowing movement. They stormed up field with Northern Ireland powerless to stop them at times.
Unsurprising considering this was a completely new defensive unit, there was at times confusion at the back for Northern Ireland, but Cathcart, Shane Ferguson and Tom Flanagan were managing to rescue situations with last gasp tackles and clearances.
Northern Ireland were struck a devastating blow just two minutes from half time with Germany's second goal and the assist once again came from the lively and surging wing back Hector.
Kroos found Hector with a delightful sweeping ball, the FC Koln man played an inviting cross into the box, Gnabry missed his effort, but the ball fell to Bayern Munich's Leon Goretzka, fighting off a challenge from Ferguson, and his tame, tame effort struck the inside of Peacock-Farrell's post before trickling over the line.
Not for the first time in this qualifying campaign, Northern Ireland players had their head in their hands in despair.
Just over a minute into the second half, Gnabry scored his second of the night to make it 3-1.
Joshua Kimmich, enjoying being the architect in the centre of midfield last night, sent Lukas Klostermann free on the right wing in and he found Gnabry in space in the box and the Bayern Munich hitman, from an angle, drilled the ball home.
This was now a damage limitation exercise as boss O'Neill, heading for Stoke this morning, watched on pensively in the dug-out.
Germany were rampaging forward at will, Kroos and Kimmich, so destructive but they had to wait until the hour mark for their fourth goal.
And Gnabry became the third German after Oliver Bierhoff (1997) and Christian Ziege (1999) to score a hat trick against Northern Ireland.
The 24-year old latched on to a defence splitting ball, used his upper body strength to leave Flanagan on the floor and calmly slotted past Peacock-Farrell.
Both teams made a change with Conor McLaughlin replacing Corry Evans and Niklas Stark coming on for Klostermann and then Goretzka, with the Northern Ireland defence failing to make the necessary clearance, scored his second, stroking it past Peacock-Farrell with 17 minutes remain.
Liam Boyce won his 21st cap when he took over from McNair. The man of the night Gnabry was given a standing ovation as Nadiem Amiri gave him a breather and Linfield hot shot Shayne Lavery was also given more minutes in the international arena.
In injury time, Brandt added to Northern Ireland's misery firing the ball into the top corner to make it six.
But despite the severe battering, the scoreline mattered little, apart from the pride of Northern Ireland manager and his players being hurt.
Germany are heading to the finals in confident mood while O'Neill's men are play-off bound next March and they are just two games away from their second Euro consecutive finals.
Germany: Ter Stegen, Klostermann, Can, Tah, Hector, Gundogan, Kimmich, Kroos, Goretzka, Gnabry, Brandt.
Substitutes: Leno, Rudy, Koch, Ginter, Serdar, Neuer, Amiri, Stark, Schulz, Werner.
Northern Ireland: Peacock-Farrell, McNair, Cathcart, Flanagan, Smith, Corry Evans, Davis, Saville, Ferguson, Thompson, Magennis.
Substitutes: Lavery, McGinn, Brown, Carson, Kennedy, Donnelly, McGovern, McLaughlin, Boyce, Lafferty.
Referee: Carlos del Cerro Grande
Man of the match: Serge Gnabry
Match rating: 7/10
Last night: Germany 6 N Ireland 1; Netherlands 5 Estonia 0.