For the longest time, Chrome has had the bad habit of consuming all available CPU when starting with many tabs (a couple of hundred), essentially making your system unusable until it has loaded all tabs.
It's pretty sad, really. Back when Opera 12 was discontinued, this worked well there - tabs were loaded sequentially, but you could still open new tabs while it was doing so. Even now the experience is sub-par in the major browsers (Chrome and Firefox. I can't speak for Edge).
I mentioned Chrome already, but Firefox is also awfully slow to start up with many tabs, even when lazy-loading (i.e. a tab is not loaded until you select it) enabled.
I've yet to try Opera 41, but at least it seems to be a step in the right direction.
Hilariously, Opera itself used to have this! I think it was one of the first browsers that had this :)
(at least that's what I remember from back in the day, maybe my memory is deceiving me)