The best downloader I have found and used that works EXTREMELY well is JDownloader 2 Beta. Which I think is actually outta beta and is just called JDownloader 2 now.
A few people have made comments like do these still exist or do they really work etc. The answer is yes. For example my internet is 150 download and 35 upload. But when viewing webpages or streaming etc, we get a "boost" of speed, anywhere from 200-250mbps until the page loads.
When you use a program like JD2 you can take 1 file and split it up into 20 different packets. When you do this your allowing a lot more of your bandwidth to go straight to that file. When I use just chrome to download from the same server, I get about 5-8mbps. When I download with JD2 I get 150-250mbps. Generally it starts at roughly 28MBps and then it drops slowly to around the 20MBps mark. That is faster then the internet I am paying for. It's a really good program and works extremely well with real-debrid. I absolutely love download managers. They also have the ability to save files if your internet cuts out while you are downloading something, pausing the download without fear of corruption and more. It's an amazing program and I have been using it for years.