Based on Collectors documentation it's as simple as:

Map<String, Choice> result =
    choices.stream().collect(Collectors.toMap(Choice::getName,
                                              Function.identity()));

Well, you want to collect Pair elements into a List. That means that you need to map your Stream<Map.Entry<String, Double>> into a Stream<Pair<String, Double>>.

This is done with the map operation:

Returns a stream consisting of the results of applying the given function to the elements of this stream.

In this case, the function will be a function converting a Map.Entry<String, Double> into a Pair<String, Double>.

Finally, you want to collect that into a List, so we can use the built-in toList() collector.

List<Pair<String, Double>> mostRelevantTitles = 
    implicitDataSum.entrySet()
                   .stream()
                   .sorted(Comparator.comparing(e -> -e.getValue()))
                   .map(e -> new Pair<>(e.getKey(), e.getValue()))
                   .collect(Collectors.toList());

Note that you could replace the comparator Comparator.comparing(e -> -e.getValue()) by Map.Entry.comparingByValue(Comparator.reverseOrder()).