After the plague of hail, Moshe tells Pharaoh, "I know that you and your servants do not yet fear Hashem Elokim" (Shemos 9, 30). Rav Wolbe (Shiurei Chumash) points out that since the pesukim that describe the creation, this is the first time that the Torah refers to Hashem with both the name Hashem and Elokim. We find this "complete" appellation of Hashem used before Adam sinned and also in reference to the end of days, when there was and will be a clear revelation of Hashem. If so, why does the plague of hail warrant the use of both names of Hashem? Rav Hutner explained that Hashem told Moshe that He would harden Pharaoh's heart - i.e. he would take away his bechira. This resembles the end of days when there will be no bechira.
Rav Wolbe elaborates by noting that we say in davening "He makes peace in the heavens." In other words the shamayim is made up of both fire and water, and Hashem makes peace between them so that they can coexist in a single entity. Similarly, fire and ice coexisted in each piece of hail to bring down a veritable piece of heaven on earth. Additionally, Rashi tells us that Hashem picked up Moshe above the heavens so that he could carry out the plague of hail. Moreover, the first three plagues originated from water and dirt - the lowest elements on earth and the second group of plagues involved the animals that walk the earth, while the hail and the rest of the last plagues all emanated from the heavens. All these indicators demonstrate that from the plague of hail and on, there was a palpable revelation of Hashem's glory, culminating in makas bechoros which was carried out by Hashem Himself. This revelation of Hashem's glory merits His full name - Hashem Elokim.
Our avodah is to gain clarity in "Hashem" - as The Creator, who is "Elokim" - the One Who watches all that we do. The more clarity one has, the less difficulty he will have in properly using his bechira. One who reaches a high level of this clarity, has tapped into the wellsprings of the end of days, a position which ultimately leads to a revelation of Hashem's glory.