Show me a time when Magic has worked against Thanos... Before you say.. Warlock.... lets remember he was doing so through the Soul Gem. Hardly normal standard magic. Plus this was before a few Thanos upgrades. Strange even says.. he can't stand up to Thanos.... Hmmm he has very good magical abilites and yet he feels it would be worthless against Thanos... Yet Loki's magic would do the trick.. lol come on. Lets not forget that Thanos has also studied black magic for years and years and thus maybe that is why strange feels as he does. Point is, Loki gets beat by Thanos and Kris arguing otherwise is amusing.
That was a clone gone bad. That doesn't trump the actual fight with Thanos standing right next to Odin when he stands down. You can't use some clones opinion to trump the actual comic itself. Thanos was losing but hadn't lost yet. My opinion always supports the books.