>>283682967
They were 10/10 vampire hunters and Alucard was far more arrogant at the time, leading to severely underestimating them. They were never able to fully kill Dracula but thing is, Alucard respects the fuck out of strength and courage. He is essentially a battle maniac with a heart. He wants a true confrontation of someone who can kill him but hates the idea of senseless bloodshed and murder and even then, if someone does, he wants to see their conviction to actually take on someone who can and will fight back. You wanna be a mass murderer, better be ready to actually try and murder someone who can kick your ass.
Van Helsing and his gang basically aroused Dracula for fulfilling all of it. They were willing to fight as someone as powerful as him, they took the challenge, they had a purpose and pulled through.
He respects that and sees the same traits in Integra. Maybe even more cause of her own conviction of refusing to bend the knee to anyone, no matter how powerful the adversary is.