diffuse work converted into concentrated work does not violate the 2nd law. Conversion of work energy into heat energy, and heat energy into work energy, is also not a violation. For nuclear fusion, you need both heat and pressure, so you can gather loads of energy that is diffused in space and simply concentrate it. There is an expenditure of energy in the process, so somewhere, there is a loss of energy in exchange for (is the cost of) the localized concentration of energy, and the universe would see a net decrease in total energy as part of the process. The process does not occur in isolation.
Net processes allow for gains on one part of the system with greater loss in another and thus do not violate the 2nd law. The total energy flux is from a higher energy state to a lower energy state.