Helsing is a notorious vampire slayer known around the world for his expertise of killing and hunting vampires. He has a special power, and is the best at what he does, but it unfortunately comes at a price. Van Helsing has no prior memory of his past life before he became a hunter, and is on a quest to regain his memory back. Similarly, in the Buffy the Vampire Slayer, she doesn’t fully understand her power and where it comes from, but uses it to hunt evil. Both Van Helsing and Buffy are always the new person in town and outsiders of society, moving city to city and have no time for anything except hunting, and even become obsessed with it. This is shown in episode 1 of Buffy the Vampire Slayer when she has to move schools because she burned her previous school’s gymnasium down. Consequently, in the movie Van Helsing, this is shown when Van Helsing has fought in so many battles and does not know how many years he has been hunting for. In Dracula’s and Van Helsing’s first scene in the movie together, Dracula remembers their previous encounter of Van Helsing killing him, but Van Helsing does not. In his past life, it is said that Van Helsing was Gabriel, an arc angel and God’s left hand man, and at some point descended to earth and became human. “During his time on earth, Gabriel fought many great battles. At some point near the 1460s he was under the service of the Knights of the Holy Order when he met Count Vladislaus Dracula, with whom he became close friends. However, during a great battle, and for reasons unknown, Gabriel murdered Dracula in 1462. For this crime, God erased Gabriel's memory.” (Gabriel). This happens in Buffy the Vampire in Season 5 episode 1 when Buffy and Dracula meet for the first time, Buffy doesn’t remember her’s and Dracula’s previous encounter just like in Van Helsing. Later, Van Helsing is tested by Dracula to regain his memory and join him by side for all of eternity, just as Dracula tries to convince to Buffy to let him turn her into a vampire and discover her true power and be by his side for all of eternity. However, both Van Helsing and Buffy resist their urges and instead finish their job and kill Dracula.
Buffy the Vampire Slayer S1 E01- Welcome to Hellmouth https://d2l.arizona.edu/d2l/le/content/563364/viewContent/4907500/View
Buffy the Vampire Slayer S5 E01 - "Buffy vs. Dracula" https://d2l.arizona.edu/d2l/le/content/563364/viewContent/4907530/View