Conference president Alok Sharma broke down in tears while apologising for last-minute changes which environmental groups say gut measures to reduce coal.
Young activist Adam Currie from Coal Action Network is furious about the lack of action on fossil fuels.
"It's gutting really, the governments of the world aren't feeling the pressure.
"It shows that the developed countries and the big polluting interests have won out over the ambition that we need.
"It shows that in these big international forums, despite all the promises, it lives up to nothing at the end of the day."
He said a failure to agree to reparations - known as loss and damage - for poor countries already being devastated by climate change was profoundly disappointing.
"That's a betrayal of millions of people suffering from the climate crisis in developing countries.
"This mess has been created by the rich countries and now they're refusing to pay their fair share."
A main point of the meeting was to try and keep warming near the crucial 1.5C mark, but countries' combined reduction pledges did not come close.
IPCC climate report author and University of Canterbury professor Bronwyn Hayward said at least 1.5 remained the global goal, which was in itself a small victory.
"The second really big issue that [is often overlooked] is that we are now finally having a debate about how we phase down or phase out, but end, subsidies and support for coal and other fossil fuels.
"That in itself is a major achievement, even if it's going far slower than most environmental organisations and scientists and communities would wish."
Other positives include pledges from groups of countries to slash methane emissions, end deforestation, phase out coal - and a surprise cooperation agreement between global giants China and the United States.
And after six years of failure, finally a compromise that will see international carbon markets established.
Rich countries also agreed to double aid to poor ones to help them adapt to climate change.
Former New Zealand climate change ambassador Adrian Macey said it was a "workman-like" agreement which was about as strong as was politically possible.
"These COPs of late have been matched to hyped up. Every COP seems to be billed as the last chance to save the planet - absurdly high ambitions.
"Because if you have those high expectations, you're always going to be disappointed."
The agreement meant New Zealand would need to announce a new strengthened emissions reduction goal next year, Prof Hayward said.
COP26 showed the world was now paying real attention to methane, and the only way New Zealand could hit strengthened targets was to start making cuts in the agricultural sector, she said.
Climate activist Cindy Baxter said the pressure was piling on the Government to act.
"We need to see the prime minister bang heads together.
"You can't rely on a minister [James Shaw] with a portfolio outside Cabinet.
"We need the prime minister to step up now. She says it's our nuclear-free moment - let's hear it."
The Government will release its climate action plan in May next year.
