Final answer:
Juan Domingo Perón was the leader who advocated for the nationalization of industry and other social reforms in Argentina, including trade unions, paid holidays, the welfare state, and affordable housing, during his presidency.
Step-by-step explanation:
The individual who encouraged the nationalization of industry, trade unions, paid holidays, the welfare state, and affordable housing in Argentina was Juan Domingo Perón. As a key figure in Argentinean politics, Perón became immensely popular among workers for his labor laws and negotiations that heavily favored them. Elected as President of Argentina in 1946, he implemented policies that supported the workers, which led to higher wages, better living conditions, and the promotion of vacations. Perón's administration also aligned with nationalist economic measures such as import substitution industrialization, further establishing his legacy in the nation's economic and social policies.