Who was the frontrunner in european exploration

The frontrunner in European exploration was Christopher Columbus.

Explanation:

Christopher Columbus was a Genoese explorer who crossed the Atlantic in 1492 and arrived on the eastern islands of America as the first European to do so, sailing under the protection of Spain.

Columbus was not the first European to visit America, as at least the Vikings had visited there before. However, his expeditions gave a starting shot to the European conquest of America and imperialism. As a result, close links were established between Europe, the Americas and Africa in later centuries.