I brew on a Bialetti Venus every day with induction. I think you are doing it wrong. I find that the awful bitter tastes come late into the process accompanied by yellow colors and bubbles/splutters. Avoid at all cost.

My method: 1) Fill the basket level. You may tap/shake any clumps to get it level but do not tamp. 2) Heat it on 1000 watts until the first drop of coffee comes out the pipe and then reduce power 400w. 3) When you notice any hint of yellow, or any bubbles/spluttering or you have enough coffee then immediately dump it into a pre-warmed mug of milk. Ideally you want to stop the process before any bitterness arrives.