Wars cause world poverty because they destroy infrastructure which cannot be rebuilt because money is put into weapons and soldiers instead.
Lack of Education
Lack of education leads to poverty because if young people don't have an education, they won't have the skills needed to improve the country's issues, e.g. lack of clean water. This leads to not enough income to support infrastructure.
Natural disasters cause poverty because they destroy infrastructure which the country is dependent on for food and industry. This is expensive to rebuild, especially with a lack of income.
One export can lead to poverty because when an LEDC becomes reliant on one product for its income, it causes an unstable economy. This leads to extreme poverty if its value goes down due to MEDCs selling it for less.