West Indies 247 for 7 (Gayle 58, Darren Bravo 53, Mashrafe 3-39) beat Bangladesh 70 (Tamim 37, Narine 3-13, Roach 3-19) by 177 runs
Scorecard and ball-by-ball details
There was promise of a contest when West Indies were restricted to 247, but all hope evaporated by the 17th over when Sunil Narine prompted a collapse that virtually guaranteed a Bangladesh defeat. Tamim Iqbal, playing his most composed knock in ten months, became the third wicket in the space of seven balls, and with that Bangladesh's chances were almost extinguished.
West Indies eventually won by 177 runs - their largest victory over Bangladesh, who were shot out for 70 - completing their first ODI series win since February 2013. They did enough with the bat, and then toyed with Bangladesh's patience with the ball.
Narine, so threatening but wicketless in the first ODI, waded into the Bangladesh batting line-up with three wickets. He set the alarm bells ringing when he removed captain Mushfiqur Rahim and Mahmudullah off consecutive balls in the 16th over.
Narine produced a delivery that bounced more than Mushfiqur anticipated and took the edge, and later bowled one that kept slightly low but went straight past Mahmudullah's bat to hit the off stump.
Tamim fell in the next over, unable to keep Roach's bounce down and gave Chris Gayle a simple catch at midwicket. From 57 for 3 it became 57 for 6. Narine then picked up his third wicket when Sohag Gazi gave deep square leg a straightforward catch.
Kieron Pollard took a one-handed catch at short midwicket when Nasir Hossain couldn't keep a half-hearted pull-shot down, making it 66 for 8.
The last wicket fell when Al-Amin Hossain was comically run-out, providing an apt finish to the shambles that is Bangladesh's batting this year.
The top order, barring Tamim, didn't put up much resistance either. Anamul Haque and Imrul Kayes gave it away early, and Shamsur Rahman is yet to show he can shine in his new No. 4 position.
Kemar Roach was among the wickets, finishing with 3 for 19, while Jason Holder had one wicket and Ravi Rampaul two. Holder bowled in a different role today, taking the new ball and attacking the Bangladesh openers, of whom he had four to bowl at. Rampaul was slightly unlucky at the start, but made it up with the wickets later on. Roach was steady, without pushing the speed gun too much, and he didn't need to.
When they were put in to bat, West Indies' innings was neither disintegrating nor taking off for a big score. It started off with Kirk Edwards continuing his struggle with deliveries slanting in to the stumps, as he was bowled by Al-Amin Hossain for a duck.
Chris Gayle and Darren Bravo then added 88 for the second wicket with the former dominating the partnership. Gayle got to his first ODI fifty in more than a year with plenty of fours and sixes as is his norm. He started off with a straight six off Mashrafe Mortaza and whenever the opportunity presented itself, in the form of a short ball or a full toss, he latched on confidently.
There was a dearth of singles, but he made it up with the big hits, with the emphasis on picking up sixes and not fours.
The likes of Darren Bravo, Lendl Simmons and Denesh Ramdin struggled to get a move on as the Bangladesh spinners bowled with a lot of control. Abdur Razzak was wicketless in his ten overs but he provided stability, with Mahmudullah and Sohag Gazi providing enough reason to believe it was a decent move to base their attack on spinners.
Bravo got to a fifty while Ramdin and Simmons failed to push on. The fourth-wicket stand between Ramdin and Simmons progressed at less than four an over at an important stage in the innings, but it hardly mattered in the end as Bangladesh's winless streak extended to 12.
Bangladesh's lack of fight with the bat has continued, and the phone number-like scorecard after Tamim's 37 will haunt the team for a long time, or at least till their next meltdown.
Mohammad Isam is ESPNcricinfo's Bangladesh correspondent. @isam84